Difference between revisions of "Sentinel / Wonder Wizard"

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==Introduction==
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{{WIP}}
  
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Sentinel, Inc. which was a division of Magnavox Consumer Electronics Company (North American Philips, or simply NAP) manufactured four models of home version pinball machines in 1977 and 1978. They used the Wonder Wizard trademark on the machines. The trademark was registered by General Home Products Corp., a division of Magnavox Consumer Electronics Company. The trademark (registration number 1066305) was active from August 5, 1976 to October 18, 1983 and is now cancelled.
+
=Introduction=
  
−
==Games==
+
Sentinel, Inc. which was a division of Magnavox Consumer Electronics Company (North American Philips, or simply NAP) manufactured six models of home version pinball machines in 1977 and 1978. They used the Wonder Wizard trademark on the machines. The trademark was registered by General Home Products Corp., a division of Magnavox Consumer Electronics Company. The trademark (registration number 1066305) was active from August 5, 1976 to October 18, 1983 and is now cancelled.
−
==Technical Info==
+
 
−
==Problems and Solutions==
+
=Games=
−
===Power Problems===
+
*Flying Aces (1977) Model number PH7730WA01 with a flying theme.
−
===Solenoid Problems===
+
*Demolition Derby (1977) Model number PH7730WA02 with a car crashing theme.
−
===Lamp Problems===
+
*C.B. Charlie (1978) Model number PH7730WA03 with a trucker/ CB radio theme.
−
===Switch Problems===
+
*Star Explorer (1978) Model number PH7730WA05 with an outer space theme.
−
===Display Problems===
+
*Star Raid (????) Model number PH7730WA06 with an outer space theme.
−
===Sound Problems===
+
*Star Explorer (1978) Model number PH7730WA15 same as above, but made by Philips Electronics for Canadian distribution.
−
===Flipper Problems===
+
 
−
===Pop Bumper Problems===
+
[[File:CB_Charlie_from_above.jpg|200px|thumb|left|CB Charlie]]<br><br>
−
===Slingshot Problems===
+
[[File:Demolition_Derby_machine.JPG|200px|thumb|right|Demolition Derby]]<br><br>
−
===Eject Hole Problems===
+
CB Charlie and Demolition Derby home model pinball machines.
−
==Repair Logs==
+
<br clear=all>
 +
 
 +
[[File:Flying_Aces_overall_view.jpg|200px|thumb|left|Flying Aces]]<br><br>
 +
[[File:Star_Explorer_full_front_view.JPG|200px|thumb|right|Star Explorer]]<br><br>
 +
Flying Aces and Star Explorer home model pinball machines.
 +
<br clear=all>
 +
 
 +
[[File:Star_Raid_Overview.jpg|200px|thumb|left|Star Raid]]<br><br>
 +
Star Raid home model pinball machine.
 +
<br clear=all>
 +
 
 +
All of the machines had the same electronics, cabinets, and playfield layout, but with different artwork.
 +
 
 +
=Technical Info=
 +
Sentinel, Inc. machines were covered by the now expired patents 4203602 (the ball is used as an electrical switch between two "hot" contacts) and 4109916 (one coil mechanically operating two devices). This was unique in that it lowered manufacturing costs by not having to use as many coil assemblies or the circuitry to drive those assemblies.
 +
 
 +
Backbox dimensions: 17" high by 22" wide by 9" deep.
 +
 
 +
Main cabinet dimensions: 46" long by 20.5" wide by 6.5" deep.
 +
 
 +
Assembled machine weight is 68 pounds.
 +
 
 +
Motherboard: # 702605-1
 +
 
 +
Display board: # 702604-1
 +
 
 +
Solenoid driver board: # 702603-1
 +
 
 +
Audio board: # 702602-1
 +
 
 +
Integrated circuits on the pc boards:
 +
*IC101 = CD4093
 +
*IC102, IC103, IC104 = 4433 led digit driver chips (obsolete and very hard to find)
 +
*IC105 = CD4013
 +
*IC106 = CD4017
 +
*IC107 = 741 op amp
 +
*IC201 = LM324 (quad op amp)
 +
*IC202 = LM380 (2.5 watt audio power amplifier)
 +
*IC203 = 741 op amp
 +
*IC204 = 741 op amp
 +
 
 +
Owner's Manual which applies to all four Sentinel machines (does not contain any schematics).
 +
 
 +
[[Media:Sentinel_manual_better.pdf | Sentinel and Wonder Wizard Owners Manual]] <br><br>
 +
[[Media:Wonder_Wizard_schematic.pdf | Gameboard and machine schematic]] <br><br>
 +
<br clear=all>
 +
Connector designation:
 +
*P1: Display/game logic board
 +
*P2: Audio board
 +
*P3: Solenoid driver board
 +
*P4: Motherboard to playfield
 +
 
 +
Coil numbers and applications:
 +
*361669001 (also known as 1669-1) has a 1N4004 diode connected across it. This coil is used in this machine for the pop bumpers, slingshot kickers, eject hole kicker, and flipper coil. A suggested modern replacement if an original cannot be located is a Williams # AE-23-800-01 or Brunswick # 55-101741. If the replacement coil does not have a diode, be sure to install a 1N4004 diode with the banded (cathode) side connected to the same terminals and wire colors as the original being replaced.
 +
*361669002 (also known as 1669-2) has a 1N4004 diode connected across it. This coil is used in this machine only as the outhole ball return kicker. A suggested modern replacement if an original cannot be located is a Williams # AE-27-1200. if the replacement coil does not have a diode, be sure to install a 1N4004 diode with the banded (cathode) side connected to the same terminals and wire colors as the original being replaced.
 +
 
 +
 
 +
[[File:Star_Explorer_raising_playfield_top.jpg|200px|thumb|left|Lifting up the playfield]]<br><br>
 +
[[File:Star_Explorer_inside_cabinet_with_raised_pf.jpg|200px|thumb|right|A look inside the bottom of the cabinet]]<br><br>
 +
Raising the playfield and looking inside the cabinet. Be careful when raising the playfield, the wires to the flipper buttons are short. There is no prop stick in the machine so you will need to make your own out of an old broom handle or pool cue stick cut to size.
 +
 
 +
<br clear=all>
 +
 
 +
=Problems and Solutions=
 +
==Power Problems==
 +
 
 +
There are two power supply bridge rectifiers on the motherboard in the backbox. BR401 (feeds the coils) and BR402 (for the logic, displays, and sound) are both type RC204-1 (2 amps @ 400 volts). It is strongly suggested to upgrade these to 8 amps @ 400 volts. Radio Shack bridge rectifier # 276-1181 will be fine to use. If the circuit breakers keep tripping, be sure to check first for burnt playfield coils, shorted solenoid driver transistors on the driver board, and shorted bridge rectifiers on the mother board.
 +
 
 +
[[File:Star_Explorer_boards.jpg|200px|thumb|right|Power transformer, breakers, and boardset]]
 +
[[File:WWSEmotherboard.jpg|200px|thumb|left|Sentinel 702605 motherboard]]<br><br><br>
 +
Motherboard showing the two bridge rectifiers as well as the master volume control.
 +
<br clear=all>
 +
 
 +
Circuit breakers and power switch are on back of machine. The 2.1 amp breaker controls BR401 (coils). One 2.5 amp breaker controls BR402 (game logic, displays, sounds). The other 2.5 amp breaker controls the 6.3 volts AC for the general illumination bulbs.
 +
[[File:Star_Explorer_circuit_breakers.JPG|200px|thumb|left|Circuit breakers on back of machine]]<br><br>
 +
<br clear=all>
 +
 
 +
==Solenoid Problems==
 +
 
 +
On solenoid driver board # 702603-1 there are five driver transistors and 5 smaller pre-driver transistors. Q301, Q303, Q305, Q307, and Q309 are the solenoid driver transistors and are "house marked" as RCA 393. These are actually type 2N6099 or NTE 331, and can be substituted with the common TIP 102 transistor, which is used in most other commercial pinball machines. Q302, Q304, Q306, Q308, and Q310 are the pre-drivers and are "house marked" as 1482. These are actually type 2N4401 or NTE 123AP transistors. It appears that the manufacturer had thought about having an additional coil on the playfield. They have empty places on the solenoid driver board for driver transistor Q311 and pre-driver transistor Q312.
 +
 
 +
[[File:WWSEsolenoidboard.jpg|200px|thumb|left|Sentinel 702603 solenoid driver board]]<br><br>
 +
The solenoid driver board showing the 2N6099 driver transistors (the large ones) and the 2N4401 pre-driver transistors (the small black ones). All solenoids operate on 24 to 28 volts DC.
 +
<br clear=all>
 +
 
 +
Transistor assignments:
 +
 
 +
*Vertical set of pop bumpers: Q309 and Q310
 +
 
 +
*Horizontal set of pop bumpers: Q307 and Q308
 +
 
 +
*Eject hole: Q305 and Q306 (also driven by IC201, type LM324N)
 +
 
 +
*Outhole ball return: Q303 and Q304 (also driven by IC106, type 4017)
 +
 
 +
*Slingshot kickers: Q301 and Q302
 +
 
 +
==Lamp Problems==
 +
 
 +
There are three "ball in play" LED's on the display board. The manufacturer left two empty spots on the board for two more ball in play LED's which would appear they thought about having a selectable 3 or 5 ball game.
 +
The game over and ball-in-play LED's are all driven by IC 106 (type 4017). This IC in turn switches on the individual LED's via a driver transistor:
 +
* Q110 (type 2N3904) Game Over
 +
* Q111 (type 2N3904) Ball 3
 +
* Q112 (type 2N3904) Ball 2
 +
* Q113 (type 2N3904) Ball 1
 +
 
 +
General illumination is 6.3 volts ac and uses common #47 and #455 bulbs in the machine. There is a 2.5 amp circuit breaker on the rear of the machine to protect the general illumination circuit from the transformer.
 +
 
 +
==Switch Problems==
 +
[[File:Star_Explorer_standup_rubber_switch.jpg|200px|thumb|left|Standup switches look like paper clips]]
 +
[[File:Star_Explorer_rollover_contacts.jpg|200px|thumb|right|Metal rollover contact strips]]<br><br>
 +
Sentinel did not use the normal rollover switches or standup switches. They used what looked like bent paper clips that touch each other as standup switches behind the rubber rings. Instead of a slot cut into the playfield for a rollover switch assembly, Sentinel used a series of three metal strips attached to the top of the playfield to act as rollovers. The metal ball completes the circuit by touching either the top to middle strips or the bottom to middle strips.<br>
 +
 
 +
The metal strips are glued to the playfield. They must be kept clean and shiny in order to work correctly.
 +
<br clear=all>
 +
 
 +
[[File:Star_Explorer_tilt.jpg|120px|thumb|left|Tilt assembly in Sentinel machines]]<br><br><br><br>
 +
The tilt assembly is a phony "ball-and-chain" setup and is not very good. It is suggested to replace this assembly with the conventional plumb bob parts available from the usual pinball parts suppliers. Doing so will make the tilt more reliable.
 +
<br clear=all>
 +
 
 +
The original START pushbutton switch was a cheap "all-in-one" unit and is no longer available. Replace the original switch assembly with a Williams # 20-9663-1 Lighted Start Button Assembly. It will come with a 6 volt # 555 bulb in it. It's up to you to choose whether or not to use the bulb, since you would need to wire the bulb to a source of 6 volt power.
 +
 
 +
==Display Problems==
 +
 
 +
The digital display on 702604 display board develops bad solder joints on the pins of the display itself. Be sure to check the soldering of those pins if display problems are being experienced.
 +
 
 +
[[File:WWboard1.jpg|200px|thumb|left|Sentinel 702604 display board]]<br><br>
 +
Look closely at the pins of the display for bad solder joints on the foil side of the board.
 +
 
 +
* IC 105 controls 100,000 digit
 +
* IC 104 controls 10,000 digit
 +
* IC 103 controls 1000 digit
 +
* IC 102 controls 100 digit
 +
* IC 101 controls tens, ones, and thousands digits through pins 1, 2, and 3 as well as pins 11, 12, and 13
 +
 
 +
<br clear=all>
 +
 
 +
==Sound Problems==
 +
 
 +
The volume control pot is soldered to the 702605 motherboard in the backbox. The shaft of the control gets banged around alot which causes the terminals of the control to develop bad solder joints on the motherboard.
 +
 
 +
[[File:WWboard3.jpg|200px|thumb|left|Sentinel 702602 audio board]]<br><br>
 +
There are several pots on the audio board. Don't play with them. Be sure to clean the foil fingers of the edge connector.
 +
 
 +
<br clear=all>
 +
 
 +
Integrated circuit IC202 is the amplifier chip that drives the speaker. It is a type LM380N and can be replaced by NTE 740A. Integrated circuit IC201 is the preamp chip and it is a type LM324.
 +
Integrated circuit IC 101 pins 4, 5, and 6 as well as pins 8, 9, and 10 control muting the sound.
 +
 
 +
==Flipper Problems==
 +
 
 +
These are old classic Stern Generation 2 flipper assemblies operating on 24 to 28 volts DC. The corner of the frame was modified by Sentinel by chopping off one corner in order to clear the outhole trough and the terminal strip. Some of the flipper parts are reproduced by Pinball Life. There is only one flipper assembly and it has a linkage connected to it to operate the other flipper bat. When the flipper coil pulls in, both flipper bats will move at the same time. Both flipper button cabinet switches are wired in parallel so that pushing either button will operate the flipper assembly.
 +
The 3" flipper bats have an offset pivot point. If using standard 3" bats, the tips of the flippers will be too close, and the ball will not be able to drain. These machines should have had 2" Gottlieb flat top flipper bats # A11242-3A Blue plus # A6888E Thin Shoe & Shaft plus Screw # HDW-632-1-1/4.
 +
 
 +
[[File:Star_Explorer_flipper_wiring.jpg|200px|thumb|left|Flipper wiring has resistor to reduce power]]<br><br>
 +
Notice the 20 ohm 25 watt resistor connected to the terminal strip. It is connected in series to the flipper coil (coil number 361669001 also known as 1669-1) to reduce power for holding. The end-of-stroke switch shorts (bypasses) the resistor during the pull-in time. Then the switch opens thus putting the resistor in the circuit to drop power for the holding function. The resistor can get very hot which is why they put a piece of sheet metal behind it to prevent burning the wood. It would be a better idea to replace this coil/resistor setup with a normal 24 volt flipper coil such as a Brunswick # 55-101725 or a Gottlieb # A-20095. Then the resistor and piece of sheet metal could be eliminated completely.
 +
 
 +
<br clear=all>
 +
 
 +
The original flipper button cabinet switches were a cheap "all-in-one" assembly which is simply not available anymore.You can replace it with Bally flipper button parts of the late 1970's vintage such as what was used on Power Play, Kiss, Playboy, etc.
 +
 
 +
'''Here is a list of Bally parts to convert one assembly:'''
 +
*(1) # C-905 Flipper Button
 +
*(1) # C-904 Flipper Button Housing
 +
*(1) # P-1566 Flipper Button Metal Mounting Plate
 +
*(1) # ASW-A10-41 Flipper Button Cabinet Switch
 +
*(2) # 8 by 1/2" long Phillips Pan Head Sheet Metal Screws (for mounting flipper button)
 +
*(2) # 4 by 1 inch long Phillips Pan Head Sheet Metal Screws (for mounting switch)
 +
 
 +
==Pop Bumper Problems==
 +
These are classic Stern/Chicago Coin pop bumper assemblies with the coil operating on 24 to 28 volts DC. There is no skirt or bumper return spring since the electrical circuit is made by the ball contacting the metal ring on the playfield and the rod & ring. With the metal ball completing the circuit, this sends a signal back to the game board to score points and fire the pop bumper coil. An improvement/upgrade would be to remove the metal ring from around the pop bumper and install pop bumper skirt of desired color, pop bumper base spring, and a conventional pop bumper spoon switch assembly. This would make the pop bumper back into a normal one.<br>
 +
 
 +
If there ever is a problem with the coil bracket, you can use a Williams # 04-10888 or B-7417 coil bracket to replace the original bracket.<br>
 +
 
 +
[[File:Star_Explorer_metal_pop_bands.jpg|200px|thumb|left|Metal rings on playfield around pop bumpers]]
 +
[[File:Star_Explorer_lower_pop_bumpers_and_hole_kicker.jpg|200px|thumb|right|Pop bumper linkages]]<br><br><br>
 +
The metal rings are glued to the playfield. The glue often fails after this many years and the ring starts lifting. The metal must be kept clean and shiny to make good electrical contact or weak pop bumper action will result.
 +
<br clear=all>
 +
 
 +
==Slingshot Problems==
 +
 
 +
These are old Stern/Chicago Coin slingshot assemblies with the coil operating on 24 to 28 volts DC. The electrical circuit is made by the ball contacting the metal strip on the playfield in front of the slingshot and the metal spring around the plastic posts. There is no rubber ring around the slingshot because of this. You can use a Williams # 04-10888 or B-7417 coil bracket to replace the original coil bracket. The driver transistor is Q301.<br>
 +
 
 +
[[File:Star_Explorer_slingshot_band.jpg|200px|thumb|left|Metal plate in front of spring band]]
 +
[[File:Star_Explorer_lower_pf_wiring.jpg|200px|thumb|right|Slingshot coil and linkages]]<br><br><br>
 +
 
 +
The metal spring (used instead of a rubber ring) around the posts and the metal plate on the playfield are two electrical contacts. The metal ball touching both at the same time complete the circuit and signal the gameboard to score points and fire the coil. The metal surface must be very clean and shiny to make good contact. Notice the glue has gone bad on the metal strip and it's lifting away from the playfield.
 +
<br clear=all>
 +
 
 +
==Eject Hole Problems==
 +
If the coil or its diode are shorted or the driver transistor (Q305) is shorted, the circuit breaker will trip. Transistors Q305 and Q306 drive the coil via a signal from IC201.<br>
 +
 
 +
[[File:Star_Explorer_sling_hole_pops_wiring.jpg|200px|thumb|left|Eject hole wiring and microswitch]]
 +
[[File:Star_Explorer_hole.jpg|200px|thumb|right|Eject hole coil]]<br><br><br>
 +
The microswitch signals the board to score points then fire the eject coil to kick out the ball.
 +
 
 +
<br clear=all>
 +
 
 +
==Outhole Ball Return Problems==
 +
 
 +
[[File:Star_Explorer_outhole_from_left.jpg|200px|thumb|left|Outhole assembly viewed from the left]]
 +
[[File:Star_Explorer_outhole_from_right.jpg|200px|thumb|right|Outhole assembly viewed from the right]]<br><br><br>
 +
Sentinel made their own outhole ball return assembly. It would appear that an old Stern plunger & link assembly may work as a replacement if the original one is worn or damaged. The driver transistor is Q303. Transistors Q303 and Q304 drive the coil via a signal from IC106.
 +
<br clear=all>
 +
 
 +
[[File:Star_Explorer_outhole_from_top.jpg|200px|thumb|left|Outhole assembly viewed from the top]]
 +
[[File:Star_Explorer_outhole_trough.jpg|200px|thumb|right|Outhole trough assembly viewed from the top]]<br><br><br>
 +
Sentinel made their own ball trough assembly out of one piece of sheet metal.
 +
<br clear=all>
 +
 
 +
=Repair Logs=

Latest revision as of 22:28, 11 April 2021

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Note: This page is a work in progress. Please help get it to a completed state by adding any useful information to it.


1 Introduction

Sentinel, Inc. which was a division of Magnavox Consumer Electronics Company (North American Philips, or simply NAP) manufactured six models of home version pinball machines in 1977 and 1978. They used the Wonder Wizard trademark on the machines. The trademark was registered by General Home Products Corp., a division of Magnavox Consumer Electronics Company. The trademark (registration number 1066305) was active from August 5, 1976 to October 18, 1983 and is now cancelled.

2 Games

  • Flying Aces (1977) Model number PH7730WA01 with a flying theme.
  • Demolition Derby (1977) Model number PH7730WA02 with a car crashing theme.
  • C.B. Charlie (1978) Model number PH7730WA03 with a trucker/ CB radio theme.
  • Star Explorer (1978) Model number PH7730WA05 with an outer space theme.
  • Star Raid (????) Model number PH7730WA06 with an outer space theme.
  • Star Explorer (1978) Model number PH7730WA15 same as above, but made by Philips Electronics for Canadian distribution.
CB Charlie



Demolition Derby



CB Charlie and Demolition Derby home model pinball machines.

Flying Aces



Star Explorer



Flying Aces and Star Explorer home model pinball machines.

Star Raid



Star Raid home model pinball machine.

All of the machines had the same electronics, cabinets, and playfield layout, but with different artwork.

3 Technical Info

Sentinel, Inc. machines were covered by the now expired patents 4203602 (the ball is used as an electrical switch between two "hot" contacts) and 4109916 (one coil mechanically operating two devices). This was unique in that it lowered manufacturing costs by not having to use as many coil assemblies or the circuitry to drive those assemblies.

Backbox dimensions: 17" high by 22" wide by 9" deep.

Main cabinet dimensions: 46" long by 20.5" wide by 6.5" deep.

Assembled machine weight is 68 pounds.

Motherboard: # 702605-1

Display board: # 702604-1

Solenoid driver board: # 702603-1

Audio board: # 702602-1

Integrated circuits on the pc boards:

  • IC101 = CD4093
  • IC102, IC103, IC104 = 4433 led digit driver chips (obsolete and very hard to find)
  • IC105 = CD4013
  • IC106 = CD4017
  • IC107 = 741 op amp
  • IC201 = LM324 (quad op amp)
  • IC202 = LM380 (2.5 watt audio power amplifier)
  • IC203 = 741 op amp
  • IC204 = 741 op amp

Owner's Manual which applies to all four Sentinel machines (does not contain any schematics).

Sentinel and Wonder Wizard Owners Manual

Gameboard and machine schematic


Connector designation:

  • P1: Display/game logic board
  • P2: Audio board
  • P3: Solenoid driver board
  • P4: Motherboard to playfield

Coil numbers and applications:

  • 361669001 (also known as 1669-1) has a 1N4004 diode connected across it. This coil is used in this machine for the pop bumpers, slingshot kickers, eject hole kicker, and flipper coil. A suggested modern replacement if an original cannot be located is a Williams # AE-23-800-01 or Brunswick # 55-101741. If the replacement coil does not have a diode, be sure to install a 1N4004 diode with the banded (cathode) side connected to the same terminals and wire colors as the original being replaced.
  • 361669002 (also known as 1669-2) has a 1N4004 diode connected across it. This coil is used in this machine only as the outhole ball return kicker. A suggested modern replacement if an original cannot be located is a Williams # AE-27-1200. if the replacement coil does not have a diode, be sure to install a 1N4004 diode with the banded (cathode) side connected to the same terminals and wire colors as the original being replaced.


Lifting up the playfield



A look inside the bottom of the cabinet



Raising the playfield and looking inside the cabinet. Be careful when raising the playfield, the wires to the flipper buttons are short. There is no prop stick in the machine so you will need to make your own out of an old broom handle or pool cue stick cut to size.


4 Problems and Solutions

4.1 Power Problems

There are two power supply bridge rectifiers on the motherboard in the backbox. BR401 (feeds the coils) and BR402 (for the logic, displays, and sound) are both type RC204-1 (2 amps @ 400 volts). It is strongly suggested to upgrade these to 8 amps @ 400 volts. Radio Shack bridge rectifier # 276-1181 will be fine to use. If the circuit breakers keep tripping, be sure to check first for burnt playfield coils, shorted solenoid driver transistors on the driver board, and shorted bridge rectifiers on the mother board.

Power transformer, breakers, and boardset
Sentinel 702605 motherboard




Motherboard showing the two bridge rectifiers as well as the master volume control.

Circuit breakers and power switch are on back of machine. The 2.1 amp breaker controls BR401 (coils). One 2.5 amp breaker controls BR402 (game logic, displays, sounds). The other 2.5 amp breaker controls the 6.3 volts AC for the general illumination bulbs.

Circuit breakers on back of machine




4.2 Solenoid Problems

On solenoid driver board # 702603-1 there are five driver transistors and 5 smaller pre-driver transistors. Q301, Q303, Q305, Q307, and Q309 are the solenoid driver transistors and are "house marked" as RCA 393. These are actually type 2N6099 or NTE 331, and can be substituted with the common TIP 102 transistor, which is used in most other commercial pinball machines. Q302, Q304, Q306, Q308, and Q310 are the pre-drivers and are "house marked" as 1482. These are actually type 2N4401 or NTE 123AP transistors. It appears that the manufacturer had thought about having an additional coil on the playfield. They have empty places on the solenoid driver board for driver transistor Q311 and pre-driver transistor Q312.

Sentinel 702603 solenoid driver board



The solenoid driver board showing the 2N6099 driver transistors (the large ones) and the 2N4401 pre-driver transistors (the small black ones). All solenoids operate on 24 to 28 volts DC.

Transistor assignments:

  • Vertical set of pop bumpers: Q309 and Q310
  • Horizontal set of pop bumpers: Q307 and Q308
  • Eject hole: Q305 and Q306 (also driven by IC201, type LM324N)
  • Outhole ball return: Q303 and Q304 (also driven by IC106, type 4017)
  • Slingshot kickers: Q301 and Q302

4.3 Lamp Problems

There are three "ball in play" LED's on the display board. The manufacturer left two empty spots on the board for two more ball in play LED's which would appear they thought about having a selectable 3 or 5 ball game. The game over and ball-in-play LED's are all driven by IC 106 (type 4017). This IC in turn switches on the individual LED's via a driver transistor:

  • Q110 (type 2N3904) Game Over
  • Q111 (type 2N3904) Ball 3
  • Q112 (type 2N3904) Ball 2
  • Q113 (type 2N3904) Ball 1

General illumination is 6.3 volts ac and uses common #47 and #455 bulbs in the machine. There is a 2.5 amp circuit breaker on the rear of the machine to protect the general illumination circuit from the transformer.

4.4 Switch Problems

Standup switches look like paper clips
Metal rollover contact strips



Sentinel did not use the normal rollover switches or standup switches. They used what looked like bent paper clips that touch each other as standup switches behind the rubber rings. Instead of a slot cut into the playfield for a rollover switch assembly, Sentinel used a series of three metal strips attached to the top of the playfield to act as rollovers. The metal ball completes the circuit by touching either the top to middle strips or the bottom to middle strips.

The metal strips are glued to the playfield. They must be kept clean and shiny in order to work correctly.

Tilt assembly in Sentinel machines





The tilt assembly is a phony "ball-and-chain" setup and is not very good. It is suggested to replace this assembly with the conventional plumb bob parts available from the usual pinball parts suppliers. Doing so will make the tilt more reliable.

The original START pushbutton switch was a cheap "all-in-one" unit and is no longer available. Replace the original switch assembly with a Williams # 20-9663-1 Lighted Start Button Assembly. It will come with a 6 volt # 555 bulb in it. It's up to you to choose whether or not to use the bulb, since you would need to wire the bulb to a source of 6 volt power.

4.5 Display Problems

The digital display on 702604 display board develops bad solder joints on the pins of the display itself. Be sure to check the soldering of those pins if display problems are being experienced.

Sentinel 702604 display board



Look closely at the pins of the display for bad solder joints on the foil side of the board.

  • IC 105 controls 100,000 digit
  • IC 104 controls 10,000 digit
  • IC 103 controls 1000 digit
  • IC 102 controls 100 digit
  • IC 101 controls tens, ones, and thousands digits through pins 1, 2, and 3 as well as pins 11, 12, and 13


4.6 Sound Problems

The volume control pot is soldered to the 702605 motherboard in the backbox. The shaft of the control gets banged around alot which causes the terminals of the control to develop bad solder joints on the motherboard.

Sentinel 702602 audio board



There are several pots on the audio board. Don't play with them. Be sure to clean the foil fingers of the edge connector.


Integrated circuit IC202 is the amplifier chip that drives the speaker. It is a type LM380N and can be replaced by NTE 740A. Integrated circuit IC201 is the preamp chip and it is a type LM324. Integrated circuit IC 101 pins 4, 5, and 6 as well as pins 8, 9, and 10 control muting the sound.

4.7 Flipper Problems

These are old classic Stern Generation 2 flipper assemblies operating on 24 to 28 volts DC. The corner of the frame was modified by Sentinel by chopping off one corner in order to clear the outhole trough and the terminal strip. Some of the flipper parts are reproduced by Pinball Life. There is only one flipper assembly and it has a linkage connected to it to operate the other flipper bat. When the flipper coil pulls in, both flipper bats will move at the same time. Both flipper button cabinet switches are wired in parallel so that pushing either button will operate the flipper assembly. The 3" flipper bats have an offset pivot point. If using standard 3" bats, the tips of the flippers will be too close, and the ball will not be able to drain. These machines should have had 2" Gottlieb flat top flipper bats # A11242-3A Blue plus # A6888E Thin Shoe & Shaft plus Screw # HDW-632-1-1/4.

Flipper wiring has resistor to reduce power



Notice the 20 ohm 25 watt resistor connected to the terminal strip. It is connected in series to the flipper coil (coil number 361669001 also known as 1669-1) to reduce power for holding. The end-of-stroke switch shorts (bypasses) the resistor during the pull-in time. Then the switch opens thus putting the resistor in the circuit to drop power for the holding function. The resistor can get very hot which is why they put a piece of sheet metal behind it to prevent burning the wood. It would be a better idea to replace this coil/resistor setup with a normal 24 volt flipper coil such as a Brunswick # 55-101725 or a Gottlieb # A-20095. Then the resistor and piece of sheet metal could be eliminated completely.


The original flipper button cabinet switches were a cheap "all-in-one" assembly which is simply not available anymore.You can replace it with Bally flipper button parts of the late 1970's vintage such as what was used on Power Play, Kiss, Playboy, etc.

Here is a list of Bally parts to convert one assembly:

  • (1) # C-905 Flipper Button
  • (1) # C-904 Flipper Button Housing
  • (1) # P-1566 Flipper Button Metal Mounting Plate
  • (1) # ASW-A10-41 Flipper Button Cabinet Switch
  • (2) # 8 by 1/2" long Phillips Pan Head Sheet Metal Screws (for mounting flipper button)
  • (2) # 4 by 1 inch long Phillips Pan Head Sheet Metal Screws (for mounting switch)

4.8 Pop Bumper Problems

These are classic Stern/Chicago Coin pop bumper assemblies with the coil operating on 24 to 28 volts DC. There is no skirt or bumper return spring since the electrical circuit is made by the ball contacting the metal ring on the playfield and the rod & ring. With the metal ball completing the circuit, this sends a signal back to the game board to score points and fire the pop bumper coil. An improvement/upgrade would be to remove the metal ring from around the pop bumper and install pop bumper skirt of desired color, pop bumper base spring, and a conventional pop bumper spoon switch assembly. This would make the pop bumper back into a normal one.

If there ever is a problem with the coil bracket, you can use a Williams # 04-10888 or B-7417 coil bracket to replace the original bracket.

Metal rings on playfield around pop bumpers
Pop bumper linkages




The metal rings are glued to the playfield. The glue often fails after this many years and the ring starts lifting. The metal must be kept clean and shiny to make good electrical contact or weak pop bumper action will result.

4.9 Slingshot Problems

These are old Stern/Chicago Coin slingshot assemblies with the coil operating on 24 to 28 volts DC. The electrical circuit is made by the ball contacting the metal strip on the playfield in front of the slingshot and the metal spring around the plastic posts. There is no rubber ring around the slingshot because of this. You can use a Williams # 04-10888 or B-7417 coil bracket to replace the original coil bracket. The driver transistor is Q301.

Metal plate in front of spring band
Slingshot coil and linkages




The metal spring (used instead of a rubber ring) around the posts and the metal plate on the playfield are two electrical contacts. The metal ball touching both at the same time complete the circuit and signal the gameboard to score points and fire the coil. The metal surface must be very clean and shiny to make good contact. Notice the glue has gone bad on the metal strip and it's lifting away from the playfield.

4.10 Eject Hole Problems

If the coil or its diode are shorted or the driver transistor (Q305) is shorted, the circuit breaker will trip. Transistors Q305 and Q306 drive the coil via a signal from IC201.

Eject hole wiring and microswitch
Eject hole coil




The microswitch signals the board to score points then fire the eject coil to kick out the ball.


4.11 Outhole Ball Return Problems

Outhole assembly viewed from the left
Outhole assembly viewed from the right




Sentinel made their own outhole ball return assembly. It would appear that an old Stern plunger & link assembly may work as a replacement if the original one is worn or damaged. The driver transistor is Q303. Transistors Q303 and Q304 drive the coil via a signal from IC106.

Outhole assembly viewed from the top
Outhole trough assembly viewed from the top




Sentinel made their own ball trough assembly out of one piece of sheet metal.

5 Repair Logs

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