Revision as of 20:22, 28 June 2012

1 Introduction

This section of PinWiki hosts general information common to all/most pinball machines.

2 Safety

2.1 Grounded 3-Prong Plug

Typical "clipped" 3rd prong on plug

If the earth ground prong of a 3-prong plug is clipped or missing, replace the plug. Many of these plugs were clipped, because some older locations where games were placed only had two-prong outlets. The 3rd prong is used to reduce the risk of shock and protect the user.

2.2 Overfusing

Installing fuses of higher values accomplishes absolutely nothing good. If the properly rated fuse continues to fail or blow, there is a bigger problem.

++++add more later++++

3 Parts to have on hand

All Machines

Bulbs/Lamps #44/47, #555, and #89 are very common types.

Electromechanical Machines

Solid State Machines

Replacement micro-switches. A long lever micro-switch is a general replacement that you can cut/form to the shape you need.
TIP-102 Transistors
IN4004 Diodes
.156 and .100 Molex header pins (the "break to size" style is the most flexible)

4 Tools of the Trade

You'll probably build your toolset as you go, but the following list is a general set that can accomplish many pinball repairs.

4.1 Mechanical Tools

Hex Key set/Allen Wrenches
Needle nose pliers - a mini-pliers set is handy
Nut driver set, which should include
- 1/4" (red) nut driver - the most common size, used for hex head screws and hex posts
- 5/16 (yellow) nut driver - used for #6 nuts
- 11/32 (green) nut driver - #8 nuts
- 3/8 nut (blue) driver - used for #10 nuts
- OPTION: 1/8" nut driver - used for microswitch nuts
- OPTION: 24" 1/4" nutdriver. If the almighty repaired pinballs, he'd use one of these.
- OPTION: low torque or torque controlled electric screwdriver and 1/4" bit. Really makes quick work of standard screws. Don't overtighten.
- Great OPTION: Magnetic tipped nutdrivers, especially for driving the hundreds of 1/4" screws into Williams playfields.
Screwdriver set. Should include #1 and #2 Flat head and Phillips head at minimum.
Security Torx Bit set. Used on newer machines for lock plates and topper domes.
Socket set, open end, or box wrenches. Should include 9/16 and 5/8 at minimum. Used for leg bolts and head bolts.
Wrenches or one 4" adjustable end wrench
- 3/8 wrench - used for tightening flipper pawls. UPGRADE: gear wrench...excellent for WPC flipper nuts
- 5/8 wrench - used for leg bolts UPGRADE: gear wrench
Pliers
High-brightness LED flashlight
Magnetic pickup tool
Magnetic parts dish
Hemostats (clamps that look a bit like scissors, for soldering)

4.2 Electrical Tools

A few alligator clip leads for testing
Digital Multimeter (DMM) with diode test function (spend more than $10.00) RadioShack or Sears are among the brands. Auto-ranging meters are much easier. With meters, you get what you pay for.
Side cutters
Wire stripper
For newer, solid state machines, a logic probe can be very useful. Fry's Electronics has several.
For Connector Work
- Connector crimpers - the cheap stamped ones are pretty much useless. See below...
- Connector pin pusher .093"
- Connector pin pusher .062"

Molex Crimper Styles

Pictured from left to right, Sargent .100 crimper w/o holder, Waldom universal crimper, Sargent 1028-CT, and Sargent 3136-CT for.156 pins shown with holder

Hand held crimpers for Molex style pins come in several styles, and as always, you get what you pay for. Cheaper types sacrifice ease of use, and quality of crimp and durability of the tool. A professional Molex crimper can cost more than $300, and is not necessary to do a excellent job of replacing the pins on a pinball machine. The cheapest type is the Waldom crimper for around $15, and is not recommended. The tool requires that you crimp twice, first for the bare wire, then for the insulation, increasing the chances of a bad crimp. Better is the $25 Sargent 1028-CT tool, which also must be crimped twice, but has better quality and is the only choice for .084 pins. Best are the Sargent type tools (3136-CT shown below) at about $95. These crimpers may have a holder for the pin, and also crimp BOTH the wire and insulation crimp at the same time, reducing the chances of a bad crimp. These tools are specific for the type of connector, whether that is a .156, .062, .100 pin. The .100 crimper does NOT have a pin holder. Replacement parts are also available for this style.

Soldering Irons

Soldering irons are used for both playfield wiring and board repair. While it doesn't matter much what soldering iron you use for playfield coils/wires/etc., it is critical that you use a good temperature controlled iron for PCB repair. Using a regular 40 watt iron for PCB repair will get too hot and ruin a board. If you think you will do any board repair in the future (and you probably will) you should get a temperature controlled soldering iron. The Weller WES51 and the older WES50 are good choices.

Portable:

These butane powered irons let you work pretty much anywhere. But they also get very hot, and can therefore easily overheat the joint and produce poor results. Don't use them on boards.

Weller P2KC Professional Self-igniting Cordless Butane Iron (Best in Class)
Portasol Piezo 75 Watt Butane Iron (Older style Weller)

There is also a type of cordless battery powered iron referred to as "cold heat" - these do not work well for any pinball application, due to the lack of control over the quality of the solder joint produced. Avoid these for pinball work.

Corded:

Weller WP25 (Utility Grade)
Weller SP23LK (Budget Grade)
Weller W60P (temperature controlled)

Station:

Weller WLC100 (Consumer Grade)
Weller WES51 (Industrial Grade)
Hakko FX-888 (Industrial Grade)

Advanced Soldering Irons

The move to lead-free manufacturing forced manufacturers to solder at a more tightly controlled, lower temperature. This requirement led to new irons that can deliver lots of heat, quickly. They have heat-up times of less than 10 seconds, and can solder larger joints than conventional irons. They have tips with built-in elements and temperature sensors. The tips show up on eBay, new and used. They are relatively expensive ($10 - $30) but last longer than regular tips. Expect to spend $200 - $400 to kit up with one of these (eBay). They are valuable if you do board work, as the fast heat delivery means the solder melts without overheating the pad.

Metcal has been making these new irons for some time, so the systems are relatively common on eBay.

Metcal MX-500P JBC - these irons really do heat up in 2 seconds (20W handpiece) Hakko FM series Weller WXT series

Ersa, Goot, Pace

4.3 Desoldering Tools

A desoldering tool will be needed when removing a component from a circuit board. Probably the cheapest and most beginner friendly desoldering tool is a vacuum type device. This is a simple suction type device that removes heated liquefied solder. It is an excellent choice for those just starting with PCB repair or those who may only do the occasional repair.

There are also irons that are similar to a standard soldering iron with a large bulb attached to the end. The concept is that the heating of the old solder and the suction to remove the old solder is done all in one motion with one tool. The drawback to this type of iron is that you could easily apply too much heat to the board when removing a component and damage the board.

Another option are controlled desoldering stations. These are the easiest and safest to use but the most expensive option.

Here's a short list of some desoldering irons.

Radio Shack 64-2098 - Vacuum desoldering tool. Great beginner choice.
Aven 17535 Desoldering Pump - Cheapest desoldering type tool, most portable.
Hakko 808 - Most expensive, corded, bulky, and easiest to use
ECG J-045 - Basic Iron with solder sucker attached. Cheapest heated/corded desoldering tool. Not recommended for beginners.

4.4 Rework Solder Stations

Pace MBT 350 (Best 3 iron station and only Class 3 approved electronics rework station. Runs micro tip soldering iron, normal soldering iron, and solder extractor simultaneously)
Pace MBT 301 (Best 2 iron station and only Class 3 approved electronics rework station. Runs 1 soldering iron and 1 solder ectractor)

4.5 EM Tools

1) Ignition points file for Tungsten contacts
2) Flexstone
3) Vendor supplied leaf switch adjustment tool
4) Homemade switch adjustment tool
5) Push-pull spring tool

Contact "points" file. You can use an automotive ignition points file from the auto parts store but ONLY on tungsten contacts. Never use this type of file on "gold flashed" contacts as found in solid state games. Doing so will ruin the switch in such a way that it will no longer be reliable.
Flexstone file. The same cautions apply here also.
Leaf switch adjuster tools.

4.6 Lubrication

In nearly every instance, lubrication should not be used. The exceptions are metal on metal mechanical points (stepper unit pivot points, stepper unit wipers, and the pivot points of very few mechanical assys.). Although Williams stated to use graphite powder for lubrication on coil plungers where aluminum or brass coil sleeves were used, it is best to just replace the metal coil sleeves with new nylon sleeves (Note: some brass coil sleeves are integral to the coil's winding, and are not removeable). A general rule of thumb is where metal makes contact with plastic, lubrication is not needed. However, if lubrication is necessary, Super Lube Teflon gel is a very good product to use. However, it should be used very sparingly. When in doubt, under lubrication is better than over lubrication.

WD-40 needs no introduction

Removal of Coin Door Sticker Residue with WD-40

In no instance should WD-40 be used as a lubricant! WD-40 is a great product, but should used as intended. It can be used for breaking apart seized screws, bolts, or associated mechanisms, but should thoroughly be cleaned off once a unit has been disassembled.

There is one other good use for WD-40 regarding pinball machines. Coin door stickers, operator stickers on aprons, and game permit stickers all tend to make their way onto pinball machines. WD-40 is a very good product which can be used to remove sticker residue.

4.7 Building a flexible power supply for bench testing PCBs

In work

5 How to Twist Wires Together Neatly

Easy as Pie...

Chuck both wires in a slow speed drill
Hold other end firmly
Engage, and watch with amazement as the wires neatly twist around each-other.

As you can see from the results below, this old technique yields excellent results.

How to neatly twist two (or more) wires together
Chuck the wires
End result
End result detail. Nice...

6 Soldering

Soldering is a simple thing, but requires a little practice and some knowledge to master. In a pinball machine, there are two kinds of soldering. One is wires to lugs - coils, lamps and switches. The other is board soldering.

NOTE: If you aren't confident with your technique, practice on something else first! Soldering is an 'art' in some respects (I like to think of it as mini-welding) so grab an old circuit board and get practicing!

6.1 Equipment and Supplies

6.1.1 The basic soldering iron

A $15 Radio Shack 25W soldering iron will work for some applications. However, a good temperature controlled, rapid heating iron is something you should consider if you do much soldering and certainly if you are soldering on printed circuit boards. Many manufacturers offer great irons. One example is the Weller WESD-51.

6.1.2 Tip Cleaner

For years, a wet sponge has been used for this purpose. Most times, the sponge is integrated into the solder station stand. Many techs now use the "wad of coils of brass" like the Hakko 599B-02 (pronounced "Hock-O"). This eliminates the need to dampen the sponge before each soldering session.

6.1.3 Solder

A wide range of solders are available. Radio Shack sells a nice .032 diameter 60/40 rosin-core solder, Radio Shack part number 64-009. For completing clean "OEM-like" solder joints, a "no clean" solder like Kester .031 diameter 63/37 no-clean solder, Kester part number 24-6337-5400, can be used. As the industry transitions to "lead free solder" (RoHS compliant), leaded solder will become increasingly more expensive and hard to find. Here is one supplier of Kester "no-clean" solder: Pinball Life Under no circumstances should Acid-core (plumbing) solder be used anywhere on a pinball machine.

6.1.4 Optional Equipment

Small tweezers or clamps such as My Handy - Great for a helping hand during soldering jobs.
Crocodile clips to make temporary connections and testing easier.

6.2 Soldering wires

We'll start with wire soldering. You'll need this skill to replace micro-switches, coils and lamp sockets. The good news is that you cannot do much damage. Just be careful about where you put the iron, watch for solder splashes or drips, and try not to overheat anything.

Here are the simple steps:

You'll need to tin the iron, the wires and lugs before you make the joint. Tinning gives you fresh solder on the joint surfaces and helps make a good connection.
Wait for the iron to heat up fully (about 700 degrees F) and apply a little touch of solder to the iron, then swiftly wipe the tip clean with your tip cleaner. This "tins" the iron.
Touch the iron to the wire. Put a tiny dab of solder between the tip and the wire, so that it melts into the wire to help transfer the heat from the iron. Feed more solder to the hot wire (not the iron) until it has a "coating" of solder. This "tins" the wire. Take care to not apply so much heat that the insulation on the wire melts.
Place the wire(s) and lugs together, and touch the iron to the joint. The solder will melt, and flow across the joint. You can add more solder at this point. As soon as the solder has run, Remove the iron and let the joint cool.

As the joint cools, the wire that you are holding will heat up as the heat conducts through the wire. You will discover that it may take 5 or more seconds for the solder to harden. The wire may become too hot for you to comfortably hold, and this is where small tweezers or "hemo-stats" are useful. Regardless of the method used to hold the wire, it is important to keep the wire from moving, until the solder takes a solid form again. If the wire is moved, you may have created what is referred to as a cold solder joint. The result of a cold solder joint will be a weak connection or a connection which will fail prematurely. A good way to determine whether or not the joint is secure after soldering is to gently tug on the wire after the joint has cooled.

Things to Know

Solder flows to the heat. If you apply solder to the iron, the solder won't flow to the wire/lug and the solder joint will be unreliable.
It takes a lot of heat to make solder turn from solid to liquid. While it is melting, the temperature does not rise. Once the liquid runs through the joint, you should pull the iron away to avoid overheating.
Some techs will "tack solder" wires to lugs, melting solder on the wire to solder on the lug. Other techs suggest that a good solder joint begins with a good "mechanical joint". They suggest that threading the wire through the coil lug (for instance) will create a stronger, longer lasting joint. Whichever method you choose, good looking solder joints begin with clean lugs and clean, freshly stripped wire.

6.3 Soldering on Printed Circuit Boards

Soldering components onto printed circuit boards is a bit more delicate than general soldering. The need for a good temperature controlled iron, an appropriate soldering iron tip, and good solder is even more important.

Solder pads on pinball printed circuit boards are delicate and can become damaged each time heat is applied to them. If too much heat is applied for too long, especially on single sided boards, the pad will lift off, making the repair much more difficult. It is better to use more heat for less time than less heat for more time.

When the replacement of a chip is necessary, it is recommended to use a chip socket (in most all instances - there are some exceptions), versus soldering a replacement chip directly onto the circuit board. The reasoning is two-fold:

Adding a chip socket reduces the amount of heat applied to a circuit board in the future should the same chip fail.
If the same chip does fail, replacement of the chip will be much easier.

When soldering a chip socket in place, skipping from side to side for subsequent joints or skipping every other pin as you solder can help alleviate the risk of heating up a small part of the board, causing lifted pads and traces. A good solderer with the proper equipment can solder a 40 pin chip socket into place on a PCB in about 2 minutes.

The best solder joint on a PCB is achieved when the solder "flows" into the "through-hole". Of course, this won't happen on single sided boards since there is no copper trace to flow to.

Checking discontinuity between chip socket positions

After a chip socket has been soldered onto a board, it is equally a good practice to check for continuity between the socket pin and the adjoining circuitry, and discontinuity between adjacent socket positions. If there isn't continuity between the chip socket and its associated circuits, check / inspect the work performed. Likewise, if there is continuity between neighboring chip socket positions, check for excess solder or foreign material creating a conductive bridge between the two.

Note: in some cases, a PCB has traces or pads intentionally tied together between adjacent chip sockets. Consult the schematics of the particular board being worked on to verify if this is the case, when two sockets are determined to have continuity.

6.4 Repairing traces or creating a "solder stitch"

Sometimes as a result of applying too much heat to a solder pad, the pad or the trace will lift. Sometimes when removing a "snap cap" from a WPC Power/Driver board (for instance), the odds of cracking a through-hole are high since installation of the snap cap originally damaged the through-hole at least some.

A good way to repair this kind of damage is to use a "solder stitch" as pictured.

Repairing Traces Using a Solder Stitch

Procedure:

Sand or scrape some of the damaged trace on both sides of the board so that you can solder the "stitch".
Twist 3 strands (or so) of copper wire together. Give yourself enough wire to work with. Usually, about 3/4" will be enough.
Place the stitch through the through-hole and bend it tight to one side to be stitched. Inserting a small "pick" into the hole will help with placement of the stitch wire.
Solder the first side of the stitch.
Flip the board over and tack the other side of the stitch.
Install the new component (or socket) and solder into place.
All done!

7 Desoldering

Methods: Solder pump, Solder braid, Desoldering station. Pro-cons of each

Desoldering parts from printed circuit boards is obviously a bit tougher than soldering parts to the board. Desoldering alkaline damaged parts

8 DIP (Dual In-line Package) Pin Numbering Convention

DIP 14 pin

The diagram at left shows standard pin numbering for integrated circuits. Pin #1 is always located at the chips "dot" or if not dot, immediately to the left of the chips "notch". The pin "legs" are then numbered sequentially around the chip counter-clockwise. This convention is observed for DIP packages of all sizes.

9 Testing fuses

Fuses are used in many game circuits to protect failure of the circuit (shorts for instance) and possible subsequent drawing of too much power through the circuit. The fuse is specified at a particular rating so that it will be the "weakest link" in the circuit. In the event of a failure, the fuse "blows" to protect the rest of the circuit.

One of the basic tests to perform on pinball machines is to test fuses. For testing fuses, set your DMM to "continuity" or "buzz".

Testing fuses while still in their fuse holder can provide a false positive reading. This happens (sometimes) as your DMM finds a path from one end of the fuse, through other game circuitry, and back to the other end of the fuse. To prevent false positives, always remove the fuse from it's holder to "buzz" it out. At the very least, raise one end of the fuse out of the holder.

This is also a good time to ensure that the correctly rated fuse is in place. Compare the spec for the fuse (contained in your game manual or on a backbox sticker) to the actual fuse. Amperage, voltage, and fast/slow blow ratings should be checked. Never use a higher amperage fuse than specified. Always use a fuse rated at least as high as the spec voltage (higher is OK), and always use the correct fast/slow blow type. If you use a higher amperage rated fuse or a slow blow instead of a fast blow, you risk alleviating the fuse of it's job being the "weakest link", and instead, your game will find the next "weakest link", possibly a printed circuit board trace or other game wiring.

Lastly, tarnished fuse holders or fuse ends, increase resistance, adversely impacting your game's power circuits. If you need to replace a fuse holder, ensure that the new holder is rated sufficiently for the application.

10 Testing a Bridge Rectifier

Testing a bridge rectifier is simple.

Four Connections to Test a Bridge Rectifier. Black/Red dots represent test lead positions.

The picture at left illustrates the 4 readings to be taken when testing a bridge rectifier.

Procedure:

Place your DMM into "diode test".
Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
Place the red lead of the DMM on each of the adjacent legs, one at a time.
A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge.
Place the black lead of the DMM on each of the adjacent legs, one at a time.
Again, a nominal reading between .5 and .7 should be seen.

Testing a Bridge Rectifier in circuit. This part of the bridge is good.

Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).

11 Testing an integrated circuit

Besides using a logic probe to test integrated circuits when the game is turned on, there is another "game off" technique that can be used.

This test works for any 74XX series IC.

Testing ICs with a DMM

Procedure:

Remove as many connectors as possible from the board being tested. The less components connected in circuit, the more accurate test.
Digital Multi-Meter (DMM) set to "diode test".
Place the red lead on the ICs ground leg. With pin 1 of the IC oriented up and left, ground will most times be the pin on the lower left side of the IC. That is, for a 14 pin IC, ground is generally pin 7. For a 16 pin IC, ground is generally pin 8. And so on... Likewise, the red lead can be connected to the general ground plane of the board. This is beneficial if testing multiple chips on the same board.
Place the black lead on each of the other legs of the IC one at a time.

Interpreting the results:

A reading between .4 and .7 generally means the leg, and the internal gates associated with it, are OK.
A reading of "short" indicates a definite problem with the chip UNLESS, that leg is tied to ground. Consult the board schematics.
A reading of "open" indicates a definite problem with the chip.
Disregard readings when the black lead is connected to either the +5v logic bus or ground.
Comparing your results against results from a known good IC (of the same kind) is a good practice.

Readings outside of this range my indicate a failed IC, or may indicate that associated circuitry is pulling the reading one way or the other. If you remove the IC from the board, you can test the IC in complete isolation. In this case, the test is nearly 100% reliable.

Like transistor testing, this test can tell you that a part has definitely failed. However, since this test is not conducted "under load", the part may test good, but fail under normal load.

12 Testing a Transistor, Silicon Controlled Rectifier (SCR) or Field Effect Transistor (FET)

A transistor is a device for amplifying current. A small current flowing from the base to the emitter causes a large current to flow from the collector to the emitter. It is a bit like a relay, where the base-emitter circuit is the coil, and the collector-emitter circuit is the switch contact. Transistors come in two polarities, NPN and PNP. NPN transistors are the most common, because they work towards ground. PNP transistors work towards positive, and are rarely used except for the power side of the switch matrix, and some voltage regulators.

When a transistor fails, the insides tend to melt together and create a continuous short. Or, the transistor may just become leaky and turn on on its own.

Transistors are distinguished from FETs and SCRs (testing these components to be added later)

Transistors are also manufactured in several "package" types or form factors. Some common package types used in pinball machines are:

TO-3, such as a 2N3055, 2N6057, MJ2955, MJ10000. Viewing component from the back side, oriented so that the legs are closest to the bottom, the case is the Collector, Emitter on the left, Base on the Right
TO-39, such as a 2N3440 as found on Bally/Stern Regulator/Solenoid Driver boards
TO-66, such as a 2N3584 as found on Bally/Stern Regulator/Solenoid Driver boards
TO-92, such as a 2N4401, 2N5401, MPS-A13. Legs arranged EBC
TO-202, such as a MPS-U45 (or replacement CEN-U45) as found on Gottlieb driver boards
TO-218, such as a TIP-36c as found on Williams WPC Power/Driver boards. Legs arranged BCE
TO-220, such as a TIP-102, TIP-107 as found on Williams WPC Power/Driver boards and MJE15030/MJE15031 found on many power supply boards. Legs arranged BCE (left to right)

Every transistor has an emitter, a base, and a collector, commonly referred to as EBC.

Exactly how a transistor is tested depends on the package type, NPN vs PNP, and leg layout.
All testing begins with your DMM set to "diode test".
Note: some DMMs will show 4xx - 6xx (vice .4 to .6 as noted below).
Note: A transistor can "test" good and still be bad!!

NPN TO-3 package (2N3055, 2N6057, 2N6059, MJ10000)

Place the black lead of your DMM on the metal case of the transistor
Probe each of the legs with the red lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor

PNP TO-3 package (MJ2955, 2N5875, 2N5879, 2N5880, 2N5884)

Place the red lead of your DMM on the metal case of the transistor
Probe each of the legs with the black lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor

NPN TO-92 package (2N3904, 2N4401, 2N5550, 2N5551, 2N6427, MPS-A13, MPS-A42, PN2222A)

Place the red lead of your DMM on the center leg of the transistor
Probe each of the flanking legs with the black lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor

PNP TO-92 package (2N3906, 2N4403, 2N5401, MPS-A92)

Place the black lead of your DMM on the center leg of the transistor
Probe each of the flanking legs with the red lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor

NPN TO-220 package (TIP-31C, TIP-32C, TIP-41C, TIP-102, TIP-122, MJE15030, 2N6043)

Place the black lead of your DMM on the metal tab of the transistor
Probe each of the flanking legs with the red lead
.4 to .6 volts is a normal reading. Readings outside of this range indicate a failed transistor
Probe the center leg with the red lead
A "short" should be seen. If not, then the transistor has failed.

PNP TO-218 and TO-220 package (TIP-36C, TIP-42/A/B/C, TIP-107, MJE15031)

Place the red lead of your DMM on the metal tab of the transistor
Probe each of the flanking legs with the black lead
.4 to .6 volts is a normal reading. Readings outside of this range indicate a failed transistor
Probe the center leg with the black lead
A "short" should be seen. If not, then the transistor has failed.

13 Testing a coil

If a driver transistor shorts on, it will cause the associated solenoid to activate at full power and stay activated. If the coil wire gets hot enough, it will burn out its plastic coating, shorting the wires and dropping the resistance to near 0 Ohms. If this happens and you replace the broken driver transistor, but you don't check the coil, the shorted coil will cause the transistor you just replaced to be damaged.

If you are unsure of the condition of the coils in a machine it is very wise to check each coil's resistance *before* switching the machine on. The human nose can be a very useful tool in diagnosing when something has burned, so use it!

Some flipper coils are "two coils in one," where they have a power coil and a hold coil. These are normally identified as having three lugs instead of two. You can treat these as two "separate" coils for the purposes of the tests below.

13.1 Testing resistance

To test a coil's resistance:

set your DMM to 'Ohms' and attach your red and black probes to the coil lugs.
If you see a reading of less than 2 Ohms, the coil has either shorted internally or there is a wiring fault. Note: Some flipper coils will read less than 2 ohms but still be fine.
Desolder the wires going to the coil lugs and check the resistance across the coil lugs again. If it reads the same value when disconnected, then the problem lies with the melted coil. If the coil resistance reads 'normal' when it is disconnected (ie the coil is 'ok'), you may have a wiring or driver transistor issue.

It is wise to check all wiring and transistors associated with a melted coil before replacing it and powering on again.

13.2 Testing for coil power

With the machine powered on:

set your DMM to DC
Attach the black lead to a grounding strap and the red lead to one of the banded side of the coil diode (if it has one).
Depending on the coil and game, you should see a reading of 20v-60v.

Please note that some games have a door interlock switch that kills power to the solenoids or may only supply power to the coils during test/game modes.

13.3 Testing the coil diode

If the coil wires are connected backwards, the coil diode will blow. If you fit a coil that is supposed to have a coil diode and it doesn't (or the diode has shorted on), you'll probably blow the driver transistor. This can lead into a vicious cycle of replacing coil diodes and driver transistors.

To test a coil diode:

Cut one of the legs and bend it up so it's disconnected on one side. Be careful not to cut the coil wire or lug.
Set your DMM to 'Diode' mode.
Place the black lead on the non-banded side.
Place the red lead on the banded side. You should see a reading of 0.5 or thereabouts.
Carefully solder the leg 'back together.'

13.4 Testing the driver transistors

In your game manual you will (normally) find a list of which transistors is associated with each coil. If you have checked the wiring back to the driver board and the coil itself, then it's time to start testing the driver transistors. See "Testing a transistor" here for more details.

14 Replacing obsolete/hard to find parts

Need to cover...
resistor/capacitor networks (SRCs)
SOIC to DIP adapters

14.1 Resistor Networks

Resistor networks were used on many pinball PCBs to both ease the manufacturing process as well as to conserve printed circuit board space. Williams System 11 MPUs have several in the "battery corrosion zone" which sometimes need to be replaced.

Resistor networks come in two styles, bussed and isolated. Isolated resistor networks will have an even number of pins. Each 2-pin pair provides the resistor value. Typically, every other pin is tied to ground. Bussed resistor networks are similar, but each resistor shares pin 1 in common. All other pins provide the resistor value. In this sense, pin 1 (usually tied to ground) is "bussed". Bussed resistor networks may be of any length; both odd and even.

Resistor Network Representations
Bussed Resistor Network
Isolated Resistor Network

A fabricated "isolated" resistor network on a Williams Hyperball driver board

Should you be unable to acquire the correct value of resistor network, you can fabricate your own.

Isolated networks are easiest to fabricate as a discrete resistor may be substituted as shown in this picture. In the picture, SR16, SR2, and SR3 on a Hyperball driver board are replaced by discrete resistors.

Bussed networks may be fabricated in much the same way, but with a resistor soldered in at each pin (except pin 1) and then all of the resistors other ends tied to pin 1.
<need a picture of this>

15 The Switch Matrix

All solid state pinball machines implement a "switch matrix." The switch matrix is comprised of "strobe lines" (generally 8) and "return lines" (also generally 8). At the intersection of each strobe and return line, an isolation diode in series with the actual switch, connects the strobe line to the return line.

The reason for implementing a switch matrix is easily understood: economy of wiring. To sense 64 switches, a total of 16 wires are required using a switch matrix. If the designers had chosen to sense those same 64 switches individually, a minimum of 65 wires would be required.

How a switch matrix works

Conceptually, operation of the switch matrix is pretty simple. The CPU commands the return circuitry to "listen" for a pulse on each row simultaneously. The CPU then commands a strobe at column 1. Any switch that is closed on column 1 will cause the signal to be propagated down the row return where the CPU will "hear" it. A return on row 1 after pulsing column 1 means that the switch at position 1,1 in the switch matrix is closed. The CPU then moves on to column 2 and repeats the same steps. After all 8 columns are strobed, the CPU then returns to column 1 and begins the whole process again. This continues as long as the game is powered on.

Note that the actual electrical circuit implementation is quite a bit more complex than this conceptual description and may be found in the particular manufacturer's section of the Wiki. Also note that a "pulse" in this context might not be a "high" signal but instead a "change in state" (from logic 1 to logic 0 or vice verse).

A representation of the Bally/Williams WPC switch matrix is shown in the picture below. The column strobes are represented by the vertical lines. The row returns are represented by the horizontal lines.

General Switch Matrix Debugging Tips Under construction...

Switch matrix problem diagnosis always begins with determining whether the problem is on the CPU or on the playfield.

To make this determination, remove the column and row connectors from the MPU. Using a 12" or so length of jumper wire, follow the process as described here.

If the problem is on the MPU, ***debug MPU*** If the problem is on the PF, discuss finding the "at fault" switch if the problem is on the PF.

16 Switch Matrix IN WORK

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'"`UNIQ--youtube-00000003-QINU`"'

File:NormalSwitchMatrixOperation.jpg

Normal Switch Matrix Operation

File:ShortedDiodeFailureInSwitchMatrix.jpg

Implications of a Shorted Diode in the Switch Matrix

17 The Lamp Matrix

Many (if not most) pinball makers used a lamp matrix to drive the game's controlled lamps. Manufacturers that used a lamp matrix include Williams, Data East, Sega, modern Stern games, and Gottlieb System 3 games (which have a hybrid switch/lamp matrix). Classic Bally/Stern games, Atari, and Gottlieb System 1 and System 80 games drive the controlled lamps with individual transistors (or silicon controlled rectifiers).

Other manufacturers' games drive lamps with individual transistors. This applies to all Bally games, Stern Electronics games, Atari games, and Gottlieb System 80 and System 1 games.

All EM's control lamps with switches on relay stacks, or wipers on disc units.

How the lamp matrix works

A lamp matrix consists of (typically) 8 column drives and (typically) 8 row returns. At each of the 64 (8x8) intersections of this 8-by-8 matrix, an isolation diode and a lamp in series, connect the column to the row. To light a particular lamp in a row, the processor sets up the row circuitry to create a path to ground for that row. The processor then "strobes" the column containing that lamp with a short pulse of "controlled lamp" power. Since the row has been set up to create a path to ground, the lamp illuminates.

The processor can light any or all lamps in a particular column simultaneously by setting up the row circuitry to create a path to ground for the desired lamps. When the column is "strobed", those lamps will light.

The processor will work it's way through the lamp matrix (column 1, column 2, ... column 8, repeat) continuously when controlled lamps are to be lit.

Advantages of the lamp matrix

Fewer wires
Sometimes easier to identify why a lamp is not lighting.

Lamp matrix problems

Single lamp out
Single lamp locked on
multiple lamps in a row
multiple lamps in a column
seemingly random lamps lighting when they should not

Typical causes

Wiring shorts
Shorted diode(s)

18 How coils are driven

Every coil will have power "waiting at the ready" at the coil lugs. If you set your DMM to DC voltage, place the black lead of your DMM on game ground such as the ground braid or the side rail, and place the red lead of your DMM on either coil lug, you should read nominal coil voltage (exactly what voltage level depends on the game system). Your DMM reads the voltage at both/all coil lugs because a coil is of course, a continuous spool of wire. Power present at one coil lug is guaranteed to be present at the other coil lug unless the coil winding has a break in it or the winding is disconnected from the lug.

All that is required for the coil to "fire" is for the ground lug of coil to find a path to ground. This is accomplished by "turning on" a transistor, or by closing a switch that creates a path to ground.

19 Flippers

How does a flipper work?: Flippers typically have two coil windings. One is a high powered, low resistance winding, used for the power stroke (initial "flip"). The other is used to keep the flipper held up, when you are holding the flipper to trap a ball. There needs to be a mechanism to switch from the high powered side to the low powered side. The high powered side of the coil is almost a dead short, and anything other than a momentary activation would cause the fuse to blow.

High Voltage flipper operation: The original flipper operation was completely high voltage, requiring tungsten point contacts at the flipper switches and at the normally closed end of stroke switches. These switches need to be filed periodically and gapped correctly for proper operation. A maladjusted end of stroke switch can burn out a coil or a fuse as well as damage the plastic bobbin the coil is wrapped around, making for sluggish operation. Tarnished and burnt contacts at any point in the system can cause a weak flipper power stroke, making for diminished game play. Additionally, there are contacts on a machine's flipper relay that may need to be cleaned to provide the maximum power to the flippers. Connectors and header pins can also play a factor in a flipper's power; heavily tarnished connections will degrade performance.

When you press a flipper button, you are actually grounding the flipper circuit, not providing the power. The power is already present at the coil's input lug. The power flows from the power supply to the flipper coil in the most direct path possible. The input lug has the solenoid power present: one wire going to one blade of the end of stroke switch, and one end of the hold winding; one end of the high powered coil's winding is attached to the other blade of the end of stroke switch.

The flipper button has one contact attached to the terminus of both flipper coil windings; the other contact is attached to ground via the flipper relay. When the flipper relay is pulled in a ground path exists for the flipper. When it is deactivated (in game over/tilt modes) there is no ground path for the flippers. When you push the flipper button, the power travels through the end of stroke switch, the high powered coil, through the flipper cabinet switch, and the relay to ground, pulling the flipper in with great force.

A small arm on the pivot point of the flipper presses against the end of stroke switch outer blade, moving it away from the inner blade. This cuts the high power to the stroke side of the coil. Because the hold coil still is getting power via the input lug, the flipper will stay in an up position as long as you hold the button in. The hold coil has much greater resistance and so does not blow the fuse or create a short circuit.

Solid State Flipper operation: Solid state flippers do not refer to flippers in any solid state machine; rather, they refer to a design in later machines (post 1989) to eliminate the traditional high powered tungsten contacted type of flipper, which was subject to degradation over time. Less maintenance is required for solid state flippers.

There are a few different designs to eliminate the high power switches used with flippers. One circuit monitors the time the flipper is held in; anything over 50-100 milliseconds continuous activation switches the power to the low side of the coil from the upper side electronically. Some designs of this nature also have a low powered normally open end of stroke switch, so that the flipper feels more like a traditional flipper. The time function of the solid state circuit only comes into play if the end of stroke switch is never detected, switching the power to the hold coil. Williams Fliptronics(tm) flippers operate in this fashion.

Another design monitors the end of stroke switch/time and pulses the power supply to the flipper to reduce the voltage during the hold cycle. This allows a cheaper coil to be used as there is only one winding on the coil. Examples of this type of PVM flipper are late model Stern games. Sometimes the pulsing of the voltage causes the flipper to buzz slightly.

20 Changing Batteries

Solid state machines have batteries to save high score and setting information when the machine is powered off. Usually these are three AA batteries mounted on the CPU board. They should be changed annually to prevent leakage that will damage the CPU board.

Batteries can be changed with the machine powered on so that settings are maintained. Some people recommend changing one battery at a time, but this is only to help ensure that the new batteries are installed with the correct polarity.

21 Coil Chart

Information on many common coils, including the winding resistance is available at http://flippers.com/coil-resistance.html

This information is helpful to check if the resistance measured on your coil is in the right range and can also help find a substitute coil that is close to the same strength.

22 Lamp Chart

Lamp	Voltage (V)	Current(A)	Candle Power	Life (hours)	Base	Typical Use
44	6.3	0.25	0.9	3,000	Miniature Bayonet (BA9)	Common GI and controlled lamp bulb
47	6.3	0.15	0.5	3,000	Miniature Bayonet (BA9)	A low-power version of the #44; reduced heat and candle power
55	7.0	.41	2.00	500	Miniature Bayonet (BA9)	Used on some EM games, high current, heat and candle power compared to #44 and #47 Not a good replacement in pop bumpers or behind backglasses (too much heat generated)
63	7.0	.63	3.0	1,000	S.C. Bayonet (BA15s)	Used in early Williams solid state games like Flash. Found in Williams games as late as High Speed; typically installed in series
67	13.5	.59	4.0	5,000	S.C. Bayonet (BA15s)	Exclusively used as flash lamps on Gottlieb (Premier) games
73	14.0	.80	.30	15,000	Wedge (T 1-3/4)	A low-power alternative for the 86 used in Twilight Zone's clock mechanism
86	6.3	.20	.40	20,000	Wedge (T 1-3/4)	Small lamp used in Creature from the Black Lagoon ramps and Twilight Zone's clock mechanism;Gottlieb Victory ramp chaser lamps
89	13.0	.58	6.00	750	S.C. Bayonet (BA15s)	Flash Lamps on many Sys11/DE/WPC
194	14.0	.27	2.00	1,500	Wedge	Whitewater Topper Lamps Can be acquired at automotive parts stores (instrument panel / dash lamps)
199	12.8	2.25	32.00	1500	S.C. Bayonet (BA15s)	Alternate for 1156 lamp
313	28	0.17	3.5	500	Miniature Bayonet (BA9)	Used for lower playfield illumination on Black Hole and Haunted House
447	6.3	0.15	0.5	3,000	Wedge	A low-power version of the 555; reduced heat and candle power
455	6.5	0.5	N/A	500	Miniature Bayonet (BA9)	Blinker
545	6.5	0.31	N/A	500	Wedge	Blinker - used in Twilight Zone, Dirty Harry, No Good Gofers
555	6.3	0.25	0.9	3,000	Wedge	Common GI and controlled lamp bulb
906	13.0	.69	6.00	1000	T-5 Wedge	Flash Lamp
1156	12.8	2.1	32.00	1,200	S.C. Bayonet (BA15s)	High Speed II beacon lamp and Creature from the Black Lagoon hologram projection lamp Can be acquired at automotive parts stores (reverse and front turn signal lamp in some vehicles)
1251	28.0	.23	3.00	2,000	S.C. Bayonet (BA15s)	Pin-Bot and Cyclone Flash Lamps
1683	28.0	1.02	32.00	500	S.C. Bayonet (BA15s)	High Speed, F-14 Tomcat, and Rescue 911 beacon lamps; Fire! flame tube projection lamp
1847	6.3	.15	.38	5,000	Miniature Bayonet (BA9)	Dimmer, longer lasting version of 47 bulb; for areas where vibration is a factor (pop bumpers, etc.)

Notes:

A "blinker" is a lamp with an internal thermal switch (a bi-metallic strip) that interrupts power to the lamp causing it to blink on and off; the cycle is usually a few seconds. These are often used behind the title on EM games. A "flash lamp" is a lamp that is purposely over-driven for a brief instant (milliseconds) to produce an extremely bright flash of light. These are used to draw attention to game features such as bonuses.
47 lamp is often used as a replacement for 44 lamps where heat is a concern for backglass or plastics.
447 lamp serves the same purpose replacement for 555 lamps.
Candlepower is measured in Mean Spherical Candlepower (MSCP)
T-3 1/4 refers shape and size, for example T-3 1/4 is "tubular", 3.25 8ths of an inch in diameter

Detailed specifications on lamps is available at http://www.donsbulbs.com . Just enter the lamp number in the "Bulb Search" field.

23 Lamp Sockets

Some later games have illuminated buttons for start and possibly other functions. These are typically located on the front of the cabinet. Instructions on replacing the lamp in those switches can be found here.

24 Fuse Table

Pinball Machine Fuse TableSome games may have different fuses and quantities

Qty	Bally EM		Qty	Gottlieb EM		Qty	Williams EM
2	5A	BR, DC coils	2	2A SB	Drop target bank	6	10A	Main, BR, coils
2	8A	Main line fuse	2	5A SB	Main line fuse	6	15A	Lamps, coils
4	10A	Coils	4	10A	Lamps
4	15A	Lamps	4	15A	Coils
Qty	Atari		Qty	Bally/Stern (1977-1984)		Qty	Gottlieb Solid-State
2	1A SB	Power supply	3	1A SB	Coils-under PF	2	1/4A SB	Displays
1	2A SB	Service outlet	1	3A SB	Main line power	1	1A SB	Coils
1	5A SB	Main power	1	3/16A	High Voltage on SDB	2	2A SB	Drop target bank
2	7A SB	Power supply	1	3/4A	Display power supply	4	5A SB	Main, coils, lamps
2	10A SB	Power supply	1	4A	12v/5v power supply	2	8A	Lamps
4	15A SB	PS, lamps, displays	3	5A	Coils	1	10A	Lamps
			2	15A	General Illumination
			1	20A	Switched Lamps
Qty	Williams L3-L7 (1977-1984)		Qty	Williams System 9-11 (1985-1990)		Qty	Williams WPC (1990-1994)
1	1/4A SB	Display high voltage	1	1/4A SB	Power supply (displays)	1	3/8A SB	Display driver board
3	2-1/2A SB	Coils	5	2A SB	Aux board	4	3A SB	Coils, flippers
2	4A SB	Sound board	2	2-1/2A SB	Coils	3	5A SB	Power supply, lamps
2	7A SB	5v power (L7 games)	2	4A SB	Coils, flippers	1	7A SB	Power supply
2	8A	Main, switched lamps	6	5A SB	Flpr, aux, cab, lamps	1	3/4A	12v power supply
2	20A	General illumination	2	7A SB	Power supply	2	8A	Main, switched lamps
			2	1/10A	Cabinet, displays
			1	3/4A	12v power supply
			2	8A	Main, switched lamps
Qty	Data East		Qty	Sega & New Stern		Qty	Williams WPC-95 (1995-1999)
3	3A SB	Coils, flippers	1	3/4A SB	Display	2	T0.315A SB	Display
2	4A SB	Coils	4	3A SB	Coils, flippers	1	T0.63A SB	12v PS F101
4	5A SB	Lamps, power supply	1	4A SB	Power supply	5	T4.0A SB	Cls,5/12v,lmps,flsh,flpr,ln
2	7A SB	Power supply	4	5A SB	Coils, lamps	1	T5.0A SB	Switched lamps, line
1	8A SB	Line, power supply	1	7A SB	Coils	1	T6.3A SB	Coils main F108
			1	8A SB	Power line, lamps	2	T2.5A	Audio F501, F502

25 Resistors

Resistors typically have a standard color coding scheme, (the exceptions are some power resistors which have the value and wattage inked on the resistor), which is used to identify the resistor's value and tolerance. The resistor's value and tolerance can be identified on this website by clicking the appropriate color bands.

26 Game Software (ROMs)

The code used for solid state games is generally stored in EPROM chips that are located in sockets on the PCBs in the head of the pinball machine. Separate ROMs are used for CPU, sound, and display, and more than one chip may be used for each. Code is updated as bugs are found and features are added. In a few cases special home versions of ROMs have been released containing more modes and special features. These home versions are set to allow free play only. In any case, it is a good idea to have the latest version of software running on a machine. Game code can be found at manufactures web sites and burned to an EPROM. Most people do not have access to a ROM burner and these chips can be ordered from many pinball parts suppliers.

Updating the software is usually as simple as removing the old chips and installing the new ones. ROMs are notched on one end. Be sure to insert your new ROM with the notch at the same end as the one you removed. ROM sockets are notched also. DO NOT depend on the labels on the replacement roms "matching" a direction on your machine! ALWAYS check the orientation based on the notches. Sometimes there is a need to have minor board modifications to allow for a newer type ROM. An example of this is the jumper installation needed on Funhouse for a larger ROM size. Check to make sure your new ROM is a direct replacement.

Take care when removing the old EPROM chip. Do not pry the old chip up with a flat head screwdriver - or use caution while working from both ends when doing so. A chip puller is the safest way to remove the old chips. When installing the new chip gently press in each end of the chip until it is fully seated. Make sure all pins are lining up with the chip sockets.

Newer Stern machines allow game code to be upgraded via USB transfer and no ROM burning is required.

27 Tuning a Game for Best Performance

27.1 Leveling the Game

One of the most important things you can do to tune a game is make sure the playfield is level side to side. Some games contain a bubble level on the apron to check side to side leveling. Do to differing floor conditions, any time a game is moved, the level should be checked. Use an inclinometer or small torpedo level to check the side to side level. An inclinometer application can be used on a smartphone, as well. Check the level on the playfield itself, NOT on the playfield glass. The playfield may not sit level in the cabinet, or may be warped. Check the the level at several points on the upper and lower playfield. Adjust using the leg levelers. After your done, make sure you tighten the locknuts on the levelers.

27.2 Adjusting the Game Pitch

The pitch of the game drastically affects game play. A steeper game plays faster. Too steep can tax the flippers ability to make ramp shots. Too shallow, slows the game down. Too shallow can also allow the ball to be redirected more by playfield irregularities, such as warped inserts. Again, due to differing floor conditions, any time a game is moved, the pitch should be checked. The proper pitch of a given game may be indicated in the manual. In the case of games which include a bubble level for pitch, the manufacturers recommendations may be marked on the level. In the case where a recommended pitch is not indicated, the generally accepted "Rule of Thumb" is 3 1/2 degrees for EM games and 6 1/2 to 7 degrees for Solid State Games. Use an inclinometer, again on the playfield itself NOT the playfield glass, to measure pitch. Adjust using the leg levelers. After you're done leveling, make sure you tighten the locknuts on the levelers.

Some players will adjust the pitch outside of "Factory" settings, to suit their taste or playing style. After playing a game for a while on the "Standard" settings, you may wish to experiment with different pitches.

27.3 Balls

Inspect the balls in a game regularly to ensure none are pitted or becoming rusty. A damaged ball has the potential to strip playfield ink in a very short time. Keep the balls clean and polish them occasionally with a soft cloth; try not to put balls back in the machine that have skin oil on them. Transfer from the cloth directly to the machine.

The more close to round a ball is the better/more wild it will play. Balls are just ball bearings, and are manufactured to tolerances up to .001%. You don't need a ball that true to put in a pinball, but if you can afford them, they would play very well. Buying pinballs from a reputable supplier is fine; a pinball costs between 90 cents to 5 dollars depending on finish and tolerance.

27.4 Adjusting flippers

Nothing impacts a game's performance more than the performance of its flippers. The entire game can be smooth playing and work properly, yet with bad flippers no one will enjoy it to its full potential. The proper rebuilding and tuning of flippers impacts a game's performance about 70% vs. 30% for all the other parts in the game.

High voltage end of stroke switches need to be filed flat or replaced and should open with between 1/8"-1/4" gap at full extension. Flipper cabinet switches need to be filed and dressed as well, provided they are heavy, tungsten contacts. Do not file cabinet switches of games which use solid state flipper assemblies. These switches are gold plated. Filing will remove the plating and ruin the switch. For those switches, draw an old business card between the contacts as you pinch them together. This will clean the contacts sufficiently. Any connector in the flipper power path should be replaced or eliminated if possible (for instance, games that use spade lugs to attach their flipper button blades should have their wires soldered directly to the blade instead). Flipper relays need to be cleaned and contacts dressed as well, and their solder mount points re-flowed.

The angle of the flipper should be adjusted to the slope of the inlane guide (if present) and the inlane guides tweaked (either by slight movement or bending if wire type) so that no ball hop off the lane guide occurs. This issue is especially prevalent on Bally games with wire guides and early Williams' solid state games with flat metal guides; the flat metal edge gets hammered over the years as well as the guide itself loosening in its mounting screws cause it to sit lower than intended. Games without inlane guides should be checked against a reference (flyer) picture to determine the proper play angle, but some leeway is permitted here in the interests of gameplay. Under no circumstances should an opposing pair of flippers be adjusted so that one rests higher/lower than the other, nor both flippers extended not be at the same height.

The flipper bat should have a slight up-down play as you pull away from the playfield at both its rest position and extended position. Swapping worn parts from left to right or the reverse can help you re-use worn parts where replacements are not available. Rebuild and redress any worn out parts if at all possible. Reverse all hacks over the years to restore the play to its original intentions.

Some mechanisms (Bally linear flipper mechanism spotlighted) benefit from having earlier style parts (plunger, link, and pawl) swapped into their assemblies for better flipper action. The linear flipper while fine when new has a fast-wearing part in the form of the nylon bearing on its lever assembly; the earlier style parts swap in place no problem and last much longer, as well as being a zippier flip thanks to the lighter mass of its parts.

27.5 Adjusting drop targets

Most drop targets are made of plastic and are made to run 'dry', i.e. no lubrication. If you must lube them, use graphite powder or a lube specifically made for plastic on metal. Note that any lube used will tend to make the area under the playfield very messy so use very sparingly if at all. The first order of business is to disassemble the drop mechanism and clean every part very, very well. For metal parts use a metal polish to make sure there are no really sharp edges or burrs to cause wear. You might have to use a small file to dull any sharp edges. Plastic drop parts polish with Novus 2 after cleaning any grease off with a degreaser safe for plastics (simple green works well). Take caution in cleaning the drop target face. If a face is stamped with artwork, most chemicals (even mild ones) will remove the artwork.

Adjusting a drop bank so that a balancing act is performed can be a bit of an art; you want the least resistance to dropping and resetting possible while still maintaining all drops resetting properly every time. There's nothing more frustrating from a player perspective than making a good shot on a drop target and it not dropping. If adjusted properly a bank can be 'swept' with an oblique flipper shot, all drops including the stubborn tending Williams and Bally drops will sweep if clean and adjusted carefully.

27.5.1 Williams

Williams targets with contacts that ride on a circuit board would benefit from a very light application of DeOxIt. The later targets that depend on a copper blade for forward tension you can use teflon lube on the copper blade; wipe it on with your finger and wipe almost all of it off. You want the least amount of lube possible. The copper blade can be bent but be careful as the blade should be flat along its length; you want JUST enough tension so the target presses forward, but not so much that the target won't fall when you hit it.

When you reassemble Williams drop banks, do not over tighten the screws that hold the metal bars to the plastic bosses - you will ruin the tension on the drop bank and possibly crack the screw boss, rendering it useless (these parts are currently unavailable new). Just snug the bar down to the drop bank and let the lock washer do its job holding it on.

Later Williams' drop banks went to a two-spring design, one to pull the target down, and one coil spring to push the target forward on reset. This design started sometime around the Big Guns era. There's not a lot of adjustment needed in this type of target other than to clean them very well, and to ensure that the rubber grommets and the washer/screw combination are not too tight. They should be tightened just enough so the target will reset properly, but not so much that the target drops slowly. The weak points of this design are the ledge the drop targets rest on, and the studs used to hold the drop target reset coil stop. Originally, a small strip of tempered, spring steel was used for the ledge. This piece of spring steel was riveted to the drop target assy. frame. If it cracks or breaks, a single target or targets in the bank will not properly reset, as there is no ledge for them to rest in the up position. Williams realized this issue, and later versions of this type of drop target assy., somewhere around Earthshaker, were made with a replaceable ledge. Likewise, the coil stops were mounted with studs integrated into the drop target frame assy. These studs can snap off flush with the frame, allowing only one side or neither to hold the coil stop in place.

27.5.2 Gottlieb

Gottlieb drop targets are the best designed and built targets in the business. As usual, Gottlieb didn't cut corners with their original design. There are 2 discrete springs used; one to pull the drops in the proper direction to reset correctly, and another to provide the correct spring tension on the pulldown stroke. Additionally, the reset mech is mounted at an angle so the drops reset smoothly and correctly. Gottlieb drops should be adjusted to reset approximately 1/16 of an inch "above" the bank's top plate. You can loosen the reset coil mounts to slide the coil into place to accomplish this. Letting them reset too high (caused when the coil mount migrates to the bottom of its travel) will tend to break off the "foot" on each drop target. Once this happens a Gottlieb drop can reset in a very awkward position, higher than it should be; a snappy ball hit when it's in this position often will snap the target in 2.

The 2-spring Gottlieb design changed during the system 80B era. This design change moved the reset coil from the outside of the drop target assy. to the underside, center of the assy. on small and single banks. Multiple reset coils were still used on banks larger than 4 targets. The benefit of the new design was less moving parts and a slightly smaller mounting footprint. However, the newer design eliminated the two spring design, and the smooth even stroke for the reset. While the targets still drop down smartly, on reset occasionally they will reset too high, or some targets will fail to reset, if the reset coil is not adjusted properly. Well beyond the time of the initial design change, some System 3 games use a combination of the old and new style drop target assys.

27.5.3 Bally

Bally drop targets come in 2 varieties - "tombstone" and "flattop". The flattop ones were designed for games that use an inline drop target assembly (Paragon, Fathom, Eight Ball Deluxe, others) or a single drop target where the ball travels over the drop target (Flash Gordon, Rolling Stones, others). The flattop targets that have a ball path over them need to be adjusted so the target top is flush with the playfield so the ball can travel over them easily. On a single drop, you can bend the foot that's under the drop target stem to accomplish this, or loosen it and move it up or down to accomplish the same thing. On an inline bank mechanism, you want to adjust the bottom foot plate to do the same thing, which can be difficult for the center targets. Some experimentation is necessary here.

For Bally flattop drops that aren't in an inline configuration you want the drop to sit very slightly above the playfield surface (1/16 inch or less) - this is so a ball will not tend to get stuck in the slot formed by the target spaces and the playfield. Adjusting the height the drops rest at can be accomplished by moving (or bending) the foot plate or adding a spacer made out of shims (cardboard, thin metal, etc.) Install the shim on the top of the bottom frame where the foot of the plastic target rests. You can use tension clips or even a paper clip to hold your shim in place. Be sure any added shims don't interfere with the operation of the targets or reset mechanism.

The thickness of the Bally drops sometimes cause what's called "bricking" of the drop targets - a hard shot to the drops will result in the ball bouncing off the target (sometimes snapping it in half!) but the drop not dropping. There are a couple things you can try to fix this, but there's no one definitive solution that works (other than swapping in a Gottlieb target bank if you can!) - some of the things you can try are shaving a minute angle into the drop shelf where the target sits at rest under tension, changing the angle of the spring, changing the tension of the spring, and moving the entire bank inside the slot as far forward as possible. Some more radical solutions over the years have been tried to fix this issue. Adding extra springs, epoxying spring steel to the back of the target, melting notches into the target with a soldering iron, beveling the under playfield area with a chisel, changing the rubber behind the targets (fat rubber makes the bricking worse), and changing the posts behind the targets to a smaller size have all been tried with varying degrees of success, but none have fixed the issue 100%.

The newness of the drop target seems to be directly proportional to its propensity to brick; the older the drop, the more it tends to drop smoother because of years of wear. This is particularly poignant with classic Stern drop targets; they are similar to Bally drops but the reset shelf is lower on the target itself; a Stern drop can be modified to work in a Bally machine, by shaving this rib off, but not recommended as classic Stern drop targets have not been available in the "chiclet" style for over 25 years.

27.5.4 Stern (Classic)

Classic Stern drops, commonly referred to as "chiclets", were originally similar to the Bally "tombstone" style, and worked well (overall the non-flattop style of drop works well in terms of non-bricking, but often a ball could be come trapped between targets). Adjusting the down position of the targets is similar to the flattops but with slightly more height vs. the playfield, 3/32" vs. 1/16". A radical solution to this if you get this problem constantly would be to glue a piece of wood cut to fit between the targets and the slot and glued into place eliminates the gap that the ball gets stuck in, but this is a very radical solution and not recommended for most machines.

The metal parts on classic Stern drop mechanisms tend to wear and need metal cleaning/polishing to be refurbished properly. Teflon lube should be used very sparingly (wipe on, wipe almost all off.... if you can see it, it's too much) on any metal to metal contact points. Any metal coil sleeves used in drop mechanisms should be replaced with the proper sized nylon sleeves instead. The metal fingers where the drop targets contact their switches need a slight bit of lube also, less than used anywhere else. The switches themselves need to be adjusted to provide the least amount of drag to the dropping finger but still also contact enough pressure to provide some wiping action to the 2nd switch contact.

27.6 Tweaking a pop bumper

Pop bumpers should be adjusted so the slightest touch of a ball at any point causes them to activate, but not be so sensitive that vibration causes them to activate. Clean the spoon switch actuator very well. If it's plastic you can use novus to polish it. If it's metal some 2000 grit sandpaper will polish it nicely. On solid state or EM machines with high voltage points, you should file the switches clean and flat. On machines with gold flashed contacts, inspect them well and clean with brasso, alcohol, or a business card wiped between the points. If any part of the gold plating is breached, replace the contact with a new one. Gold plated contacts with missing plating will never be 100% reliable again.

Adjust the position of the spoon switch underneath the skirt's actuator so that the pin sits naturally in the center of the spoon switch. The spoon switch bracket has oblong mounting holes for exactly this purpose. To see if the pin is in the center, you can press up on the spoon switch from the bottom - if the skirt pin moves, it's not centered. Once it's positioned in the center, tighten the switch bracket mounting screws. Now, using a contact adjuster tool, adjust either the spoon blade itself (for metal ones) or the blade that provides the tension to the plastic spoon so that there's barely tension on the actuation pin (the softer this adjustment, the more sensitive the pop bumper will be). You want enough force so that the spoon re-centers the pin, but not so much that anything other than a hard ball hit activates the bumper. With the playfield raised you can activate the pop skirt by hand to see how much to adjust the spoon. It takes several tries to get this right, but it's well worth taking the time to do this.

Adjust the second blade to between 1/16"-1/8" gap between the contacts of the first blade. This will vary depending on if the machine uses high voltage activation of pop bumpers or not. You want the gap close enough so the pop is sensitive, but not so close that other mechanisms in the machine activate the pop. A good way to test this is to adjust the switch, then with the playfield lowered, make a fist and pound on the playfield in the area of the pops.

Some machines that use direct activation of pops might benefit from wiring in a Gottlieb pop bumper driver board. This applies mostly to Gottlieb System 1 solid state machines, but could also be used on some early Williams games as well as specialized purposes on other games. Basically, high voltage activated switches can pit and arc; generally, they require a slightly larger gap to ensure the contacts do not weld together from the arcing. Using a pop bumper driver board on this type of bumper with the actuation contacts changed to gold flashed type allow a closer switch gap, and the board provides a solid activation regardless of how hard the skirt was hit.

A specialized purpose for a pop bumper driver board would be on a Stern 9 Ball, for the lone pop at the top. Bally/Stern machines do not have the ability to fire more than one momentary solenoid simultaneously; this comes into heavy play on 9 Ball as the drop banks reset and drop their targets. It is possible for the top pop to not fire while this resetting is going on, especially if the game is set to require both 3 bank drops to reset to advance the bonus multiplier. The scenario is this: You drop both banks and the ball hits the pop.... with a thud. You receive score for the hit, but the pop doesn't fire because the 2 3 bank drop targets are still resetting. Changing the pop to activate with a pop bumper driver board removes the hardware limitation from the equation, as the pop is able to activate on its own; the mpu still scores the pop as a secondary switch gets added similar to Gottlieb System 1 games or early williams games.

For a while Wico made a plastic pop bumper assembly that used a plastic rod and ring combination. This was used on their game Af-Tor and also on Stern machines starting around Cheetah to the end of classic Stern production. This plastic rod and ring weighs much less than the metal assembly normally used, and can be swapped into the metal type with a little effort. The resulting quicker reacting pop is amazing in its smoothness and reaction time; you will get much better pop action with this substitution. It works even better than putting a stronger coil in the metal ringed pop bumper assembly, which will also pop the bumper quicker, but the moving mass of the metal rod and ring still make that combo slower reacting. Game plan may have used this plastic combination for a while also, as did Pinstar's Gamatron conversion kit.

27.7 Tuning a spinner

Nothing beats a solid spinner hit, spinning and racking up points at a furious pace. On the flip side, nothing sucks the enthusiasm out of a nice shot more than a spinner weakly spinning a few times lethargically, adding a couple points to your score. There are a couple tricks and techniques to make your spinners spin quick and long.

First, disassemble the spinner and clean all gunk off the support wires. The cleaner a part is in general the smoother it will operate. Polish the contact points of the support wires with 2000 grit sandpaper and a metal polish such as Brasso, or even Novus 2 (a plastic polish, but will work for this application). You want the support wires as smooth and round as possible. Then, using a very small round file, dress the holes in the spinner bracket so there are no rough edges both inside the hole and on the outside. Smooth is the key here.

Reassemble the spinner with one plastic disc against the spinner body, the below-playfield actuator wire, then another plastic disc towards the outside of the spinner. The discs and actuator wire shouldn't be 'snug.' There should be a little room for the wire to twist slightly if needed. The spinner should rest with a very slight forward cant, where the top of the spinner is slightly forward of the bottom. Adjust this by bending the spinner wires in the bracket by pushing up or down on the spinner flag itself. If you have the spinner adjusted perfectly perpendicular, the spinner can and will stop 'upside down' on occasion, locking the switch on.

Take some Teflon lube gel on a toothpick and put just a touch of it at the metal to metal contact point in the spinner bracket. Move the spinner back and forth and spin it to distribute the lube evenly. A simple rule of thumb with the lube is if you can see any, you used too much. Less is more here.

Adjust the switch blade so the spinner activates near the peak of its spin; you want it to kiss the stationary blade just slightly, with a very slight deflection. Another trick to consider is to change the height of the posts (or add spacers/washers) the spinner bracket rests on to raise the bracket slightly. The more to an edge the ball hits the spinner, the more energy is imparted to the spin. This is also another reason for the slight forward cant on the spinner.

A spinner can get up to 200 spins with one solid hit depending on the machine and flipper strength, well worth tweaking so it performs at its peak.

27.8 Tweaking Tilt Mechanisms

Most would ask why you would want to tune a tilt mechanism. Like it or not, tilt is part of the game of pinball. Unless you remove your tilts entirely, you want them to activate in a fair, consistent manner. There's nothing worse than playing a spirited game and tilting because a solid hit one time doesn't tilt, but yet a light hit later on tilts your ball.

Disassemble the tilt mech and clean everything really well to remove the gunk and grease. Use a metal polish such as Brasso to polish every part of the mech: The plumb bob, the wire, the brackets (both the top bracket and the round lower bracket). When you reassemble the mechanism, the position you put the plumb bob in makes a huge difference in how the tilt operates. Almost all parts manuals picture the plumb bob inverted (small side down) ABOVE the actuator ring, but almost all games have the bob BELOW the ring instead. Each position causes the tilt mechanism to behave differently.

The inverted position allows quicker recovery after a tilt; the rod stops moving quicker as the weight is closer to its pivot point. If you like your tilts tight, raising the challenge, the inverted position is the one to use as you can adjust the tilt to a hair level, but not so much that you tilt subsequent balls on a tilt. The disadvantages are that you have to remove the ring to insert the bob correctly, and that if the bob ever loosens up, it will just sit on the ring causing a non-playable machine.

The "normal" position does not have the issue just described; if the bob falls off, you end up with no tilt. Because the weight is farther along the rod, the tilt adjusted this way takes longer to recover after hits and may in fact swing for a very long time (2 minutes or more depending on the force imparted).

Regardless of the bob position chosen, you want the bob to be centered in the ring assembly. This can be accomplished by moving the ring if it has slots to do so, or by bending the hanger bracket the rod is suspended from. Sometimes you can flip the ring assembly upside down to obtain a better profile for the bob and ring to meet.

Shaking a pin is a part of the game, and possibly the greater factor in making you a better player. If you can impart force to the ball through shaking on a tight tilted machine, you will find yourself a much better player in all situations. Anyone can brute force manhandle a machine with no tilt; it takes skill and finesse to do so on a machine with a hair tilt.

27.9 Cleaning and Adjusting Rollover Switches

Rollover switches should offer little resistance to the ball rolling over them. A ball hang up should never occur on a rollover switch wireform; if it does, the tension on the blade is too great and needs to be backed off. The contact points should be adjusted so the contacts kiss with a very slight wiping motion, and release smartly (to prevent duplicate hits from switch bounce).

Only clean gold flashed contacts with a business card, Brasso, or alcohol. Never ever file gold plated contacts. Once the gold plating is breached, the switch will never be 100% reliable again. Often early solid state games up until 1984 or so have had their plated switches filed by the original operator who didn't think the warnings in the manual and often printed on under playfield labels to NOT file the switches applied to them. Inspect all switches to see if this has occurred and replace any filed contacts with new.

Clean the switch wireform actuator well by disassembling it and polishing it with a metal polish such as Brasso. Even though the wireforms are a metal to metal contact, you do not need to use any lubricant on it as it is not a tight metal to metal contact, nor does it need the reduced friction to operate smoothly.

The switch blade tension should be enough to hold the wireform up but allow it to depress smoothly with any speed rolling ball. Switch blades with bends and kinks in them from improper adjustment should be replaced or straightened as much as possible, and any missing insulating fishpaper should be replaced. If a dead stop blade (has a sharp bend in the middle) is on a switch adjust that instead of adjusting the switch blade its' stopping instead.

27.10 Tweaking lane guides

Lane guides are bent pieces of wire that feed inlanes/other areas of the playfield. They are also formed by plastic hoods that fit over posts, to form channels for the ball to travel. They do not require much maintenance at all, but there are a couple of things to check to ensure they are attached properly and feed the ball in the correct direction.

The plastic hood over post type doesn't really have any adjustments involved - you need to make sure the posts are held fast to the playfield. If they are lose at all, fill the mounting hole with some kind of wood filler (hardwood dowels and glue works well) and do not over-tighten the mounting screw when you reinstall. For really bad holes or posts that just get hammered (for instance, near pop bumper nests) you might want to consider replacing the wood screw with a machine thread screw and T-nut underneath the playfield. Often lamp wiring would get in the way of this however so check carefully before you upgrade.

The lane guide can be made to play differently depending on what rings you install on them. A good option is to put a slightly fatter ring on the top post of the guide so you can get bouncier action if you need to shake to get a certain lane. The fatter rubber closes off the lane space slightly, but it makes it easier to nudge to move the ball around, essential on older games without lane change or many, many lanes at the top. A tighter ring can be used on the bottom post of the guide to allow the ball to travel back UP through the lane easier, usually from a lucky pop bumper carom.

Wire lane guides are usually found directing the ball towards the flippers (inlane guides). The mounting holes can be egged out and again, can be filled and drilled. No glue is needed to hold the wire guide itself in, it's held by friction so when you drill the hole, go one drill size smaller than needed and press fit the lane guide in. Some wire guides have tangs that help hold the guide in correctly.

The wire guides that feed the flippers are especially important to have their angle adjusted correctly. You want to avoid a hop as the ball transitions from wire to flipper bat. You can put a very slight bend in the wire's vertical orientation to tweak this transition. The best way to bend it is to remove it from the game and bend it slightly with pliers; do not try to tweak this in the game as it puts undue stress on the mounting hole.

Another type of lane guide is a flat steel type guide used in an orbit or passageway back to the top of the playfield. Not a lot to tweak here but check that the mounting plates are not cracked and the screw holes are tight. Some guides have some adjustment built into them to tweak their positions. (Whirlwind and Flash are two examples that have this type in their shooter lanes.) If you find you need to tweak the position of the lane, fill the old hole completely with a hardwood dowel and glue, position the guide appropriately, mark and drill a new mounting screw. You can also use a dremel or similar to grind out a slot making a normally non-adjustable guide adjustable. The left lane guide above the upper left flipper on Eight Ball Deluxe is an example of a guide that almost always needs tweaking to avoid a flipper bounce action on a ball coming down the left guide, spoiling your cross-playfield shot aim.

Some early Bally and Stern games have a plastic inlane guide that becomes malformed or has its tip broken off. You can cut a replacement piece out of clear lexan to replace these. Cut the replacement piece as if you were cutting the entire piece of plastic, and attach it underneath the existing plastic. Another trick for the plastic lane guides is to embed a small wire guide in the appropriate position underneath the plastic guide. This is not as seamless as the clear plastic method, but it does play very well and avoids any headaches mounting the double layer of plastic.

27.11 Rubber? I hardly knew her!

There used to be only one type of rubber available for all pinball machines - a soft gum rubber that was off-white in color, but was very bouncy and gave good ball action. Today, most rubber is available in either stark white or black, and various colors. In general, black rubber plays harder (i.e. less bounce) than white rubber, but that's not always the case. You have to try rubber rings from different makers to see how they play. If you like a more controlled type of gameplay, the harder less bouncy rubber might be for you. If you like the randomness imparted to the ball by bouncier rubber use a different variety. The soft gum rubber if you can find it is incredibly bouncy, and because of the stickiness of the rubber will impart more spin to the ball, truly making it wild.

Whatever rubber you end up using, there is still some variety in sizing and mounting. You can change the way your game plays by changing the size of the rings used; go one size smaller and hard shots to that rubber will rebound harder accordingly. Fatter rubber on mini posts will make shots tighter and harder, but also allow for more nudging action. Changing the type of ring to a different type can affect vastly how the game plays - if you like more pop bumper action for instance off a rubber, you can change where the rubber mounts (i.e. which posts surrounding the pop) to have a larger expanse of rubber vs. not. Don't go so far as to add new posts in to accommodate the new rubber position, unless you're really sure that's what you want. Keep in mind if you go with tighter rubber you might have problems keeping the posts mounted in the playfield, and may have to move to a machine threaded screw instead if the tension is too high.

27.12 Plungers

Never run a plunger without a rubber tip on it. (It will mushroom out very quickly necessitating filing or hacksaw cutoff of the tip.) The plunger itself should be centered with respect to the ball track, and forward enough so the tip holds the ball forward of the playfield lip. Sometimes plungers get bent because people lift the machine by the plunger; it is best to replace the plunger in these cases.

The barrel spring on the outside of the plunger varies in length, new ones are generally too stiff for the plunger to sit at its optimal position. You can mash the new springs in a vice to shorten them a bit. Do not run a plunger without the proper springs installed as it will damage the escutcheon plate on the cabinet, either denting it in the case of metal ones, or cracking it in the case of plastic ones.

There are screws holding the plunger's position in place, loosen slightly so you can slide the mechanism around to get the best positioning. Tighten each opposing side a little at a time so you don't cant the mechanism to one side or the other, and don't overtighten it as that will put dents in the wood of the cabinet.

Make sure the spring you are using on the inside is the proper one for your game. Some games require a different tension to allow skill shots to be made (Whirlwind and Twilight Zone are 2 examples). Some games need a very strong spring to launch the ball properly (Pinbot and Taxi). When replacing the inner spring, get rid of the weaker "C" clip that holds it on and replace with an "E" clip, which is stronger and easier to install/remove.

27.13 Coil Sleeves

Older games used aluminum coil sleeves to guide the mechanism's plunger smoothly into the coil. The function of a coil sleeve is to reduce the distance between the solenoid coil bore and the mechanism plunger, resulting in more precise action. An upgrade that can be done to aluminum coil sleeves is to replace them with more modern nylon ones. Nylon has self-lubricating qualities that make it ideal for this usage. No lube should ever be used on any solenoid plunger. It will gum up over time and cause weak mechanism response and a nice mess for the next person to clean up. Any machine with lube used in the past on its plungers should have the mechanisms disassembled, its metal parts cleaned with brake cleaner or isopropyl alcohol, and reassembled with a new nylon sleeve cut to the proper length.

To cut nylon coil sleeves to length use a junker plunger in the center and a pipe cutter (available at most hardware stores). Tighten the cutter a little at a time to ensure the smoothest finish possible on the coil sleeve; don't try and make the cut in one go as that will result in a rough edge to the sleeve. Smoother is always better in a mechanism employing solenoids and plungers. File off and dress any sharp metal edges on a plunger that could snag the coil sleeve as it moves in the solenoid. If a coil plunger is particularly mushroomed, replace it.

27.14 Connectors and Soldering

Anytime an electrical part of a machine has intermittent operation suspect any connectors in its power chain. Any connector in a power chain at its best adds a minute amount of resistance to the power flow. Jones plugs' connectors can be cleaned and polished on the older EM machines; newer solid state machines you can try and polish the pins, but the best thing to do is replace or eliminate the connectors if you can and they are causing problems.

Often on solid state boards the male header pins crack from usage fatigue. Resoldering the header pins will fix this issue and while it's not strictly necessary to replace the header pins, it wouldn't hurt either. Tug on and inspect all connectors to ensure the wiring is crimped tightly into the pin. Any loose wires should have their pins replaced with new properly crimped pins. Do not use solder on a crimped pin connector; it changes the temper of the connector pin which allows oxygen to penetrate the wire bundle, allowing oxidation.

If you have some microswitches that use a spade connector, consider removing the connector and soldering the wire directly to the lug. The spade connectors were used on the wiring harnesses at the factory to speed production, not for any reliability concerns. Any connector added to a circuit introduces an unnecessary possible failure point. Any trouble shooting involving a circuit with a connector should have its connectors inspected very carefully as a first step.

27.15 Slingshots

Pull the sling plastic and rubber off the slingshots. Make sure the posts are tight to the playfield, filling any loose ones or changing them to machine threaded screws into T-nuts. It's very common for the sling rubber over time to pull the posts towards each other, and the sling plastic being depended upon to hold them apart. This is not desirable at all.

Adjust the standup switches so that the blade that touches the rubber is barely touching it. You don't want the blade adding any tension to the sling rubber itself. The secondary switch should be as close as you can make it to the first, as long as both blades are parallel. This is a very critical adjustment to make as you have 2 switches acting together, and you want one activation, not multiples as the rubber bounces back.

The size of rubber you use on the sling makes a huge difference in how it performs. Tighter lets you get the slings more sensitive, but can also limit how much the sling can move. Too loose will cause myriad problems getting the switches adjusted correctly.

Sometimes there are nails straddling the sling actuator arm; the purpose of these nails is twofold. First, they help support the sling plastic in the case of sagging, so it doesn't hit the actuator arm. Secondly, it prevents the sling rubber from pressing back really far causing a weak sling. (The switches should never activate that far back, either - this would make for a very unresponsive sling).

It is worthwhile to remove the sling arm and clean it really well, and to check for wear. You will usually see some slop in a sling mech; if it's excessive power will be lost laterally on activation. The only remedy is to replace it, or try and find small nylon washers to hold it true. Use a small bit of teflon lube on the pivot point. As usual, wipe it on and off. If you can see it, it's too much.

Make sure the sling arm is held tight to the playfield, filling and drilling as needed. If there is a scoring switch attached here, make sure there's a fiberboard spacer between the metal blade and the actuator. Adjusting the scoring switch can be problematic as there's a fine line between not scoring and scoring twice (as the switch blade bounces).

27.16 Standup/stationary Targets

Remove the target and inspect well. You can clean grease off the target with a pencil eraser or novus 2. Some standups would benefit from having a piece of weatherstripping foam added if not already present. (Any standup that gets hit with lots of force needs a foam block). Early solid state Bally, Stern, and Gottlieb games can benefit from a switch capacitor being added to help their performance. The switch capacitor lengthens quick hits to the standup so the MPU board can read even a very fast switch closure.

Make sure the mounting bracket isn't bent so the target leans backwards - this will cause airballs and broken plastics. If anything the target should be angled slightly forward to help prevent this. Some machines would benefit from a brace on the back of the target to minimize bending.

Any standup with gold plated contact points should be inspected for filing - if the gold plating is breached or gone, replace the contact points. Make sure the target bracket is held onto the playfield securely, fill and drill any egged out mounting holes. Inspect the switch blades that make up the target and straighten any out that are mangled.

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+[[Image:NormalSwitchMatrixOperation.jpg|200px|thumb|left|Normal Switch Matrix Operation]]<br>
 [[Image:ShortedDiodeFailureInSwitchMatrix.jpg|200px|thumb|left|Implications of a Shorted Diode in the Switch Matrix]]
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Difference between revisions of "General"