Leon Borre Data East CPU Board Repair

Data-east repair CPU-board.

Introduction;

There are a few different versions of the Data-east CPU's. But for this " repair manual " only one difference is significant, and that is witch type of Eprom is in location 5C. There are two possibilities,its a 27512 or a 27256. We will always use a 27512 eprom . The jumper J4 or J5 determine wich type of game eprom is used in the game the jumper J4 is present for a 27256 and the jumper J5 is in place if you have a 27512. Always place the test eprom in socket 5C . The jumper has no influense on the working of the test eprom. It works fine wherever jumper is placed .

The goal of this article is to explain the basic repair of the cpu-chip circuitery , the memory chip and the 6 connected PIA's. These PIA's (6821) are used to send all signals to the external circuits, to the dot-matrix, coils, lights, and via the switch matrix to all switches. The PIA on 8H is the source of the switch matrix. When the CPU and PIA's are ok, it's almost certain that your pin will start and you can troubleshoot further (if necessary) with the internal test-functions of the pinball. I assume your voltages are ok, which you can check with a dmm. So don't forget to do this !! You only need to have 5 volts for the cpu to start.

Start.

So your pinball does not start, but you checked the voltages and they are ok. Look at the led's first, three in the middle off the cpu board on the right. The 5 volt led should be on, and probably the PIA led too, sometimes also the blanking led but not very often.

You can see the leds in the middle of the cpu-board.

You have to take the cpu-board out of the pinball. If you're not sure where the connectors have to go, don't forget to label them ! Once the cpu board is out of the machine, you'll have to connect it to 5 volts. This is easy, on the left top there's a jumper labeled ground and another labeled 5 volt. Connect 5 volt to this last one, and ground to the other one.

On the top right corner of the battery holder you find the jumpers to connect 5 volts and GND..

Now you need my test-eprom which you plug into socket 5C. Remove the program-rom that's in there first and be sure to store it safe! The test-eprom contains a program that does not lock-up, and will switch all outputs of all 6 PIA's to high ( 5) and then low (gnd). By checking the outputs of the PIA's go up and down (use a dmm or logic tester) and you'll see what PIA or pin is malfunctioning. If none of them work then the problem is earlier on the board...We connect a control led directly to the adress line 6 ( pin 15) of the cpu chip, this led will flash if the test program runs ok.The PIA-led present on the cpu board is connected on the PIA in 11B and when the program runs,and this PIA is ok, it should flash. The same goes for blanking led, which will have very short flashes.

The control led is a simple led in series with an 1000ohm resistor and has two connection grips.

Isolate the connections at the led ( not done on this photograph..) and try it out as follows; connect the red grip to 5 volts and the green to ground. The led sould light up if not change the two led leads. In test mode the led is connected with the red grip to 5 volts and with the green to pin 15 of the cpu chip ( IC 3D)

The test-eprom you'll need is in an Eprom 27512 and the program can be downloaded here ...for 27512, zip file .... if you do not have an eprom-programmer you'll have to ask someone who can do it for you...

Attention, since 10/5/2005 there is a new version of the test eprom. Using the improved memory test. To recognise if you have an old or new image , read the image with "WORD" between the strange signs you will find VERSION 5 that means you have the newest version. We need only ONE 27512 eprom. The test eprom is always in socket 5C. The placement of the jumper can be in J4 or J5 what ever , it always working fine.

So the program is in 5C and the 5 volt connected. If you're lucky the control led will flash. Then start checking the outputs of all PIA's, pins 2 to 17 should go from 0 to 5 volts (which also can be seen with a dmm). There are some exceptions however ! The PIA of switch matrix on 8H has pins 2 to 9 as input. To check these you'll have to connect all pins of CN10 to ground. Use some alligator clips to ground all these pins of CN10, and then the pins (2-9) of the PIA in 8H can be read. And the other exception is that the PIA on 11B has pin 9 forced to ground and cannot be read. If you find a pin that's not flashing, short it with the (working) pin next to it, if he also starts flashing then the PIA is broken; if they both stop then there's somewhere a short on the output or the PIA itself is broken... You'll have to try to find the short or replace the PIA.

Worst case scenario

If the program doesn't work at all, we'll have to go to the source and that's the CPU chip 6802 itself. Replace it, that's the easiest. Still the problem ? Check these pins: 2, 4, 6 and 40 should be positive (around 4 volts). On pin 39 you can find the clock signal, on pin 5 the VMA signal, and on pin 37 signal E (syncro for external elements) these should be 2 to 3 volts (measured with a regular dmm. These are alternating signals, here you have some pictures of them.

Clock signal ................................... and the VMA signal

E signal: ......

If one of these 7 signals is different then you have found the problem. Use the schematics to check where this signal comes from. This may be no problem as the circuits are not very complex.

The long way... or not!!

What's left are the other outputs of the cpu: addresses (pin 9 to pin 25, except pin 21 which is ground!!) and data (pin 26 to pin 33), but also the selection circuit of the test-program chip 5C and the selection circuit chips of the PIA's. If the test program does not work, it is possible that the test-chip is not found, or because the pia's are not found.( no selection...)How to solve this ? It's very simple !!!

It's useless to give you the signals which you would find when everything works, because it doesn't. So what you have to do, it remove the test-chip out of the cpu-board and restart . The cpu will now work WITHOUT a program, and will execute NOP's (Non Operative instuctions), it runs through all it's addresses starting at 0000-0000-0000-0000 to FFFF-FFFF-FFFF-FFFF and again and again. With this we can continue to test: all address pins should move, which are pins 9 to 25 (except pins 21 which is ground) and should mesurer about 2 volts. Now you have checked your address lines. Do the same for the address-lines-buffers, IC's 6C and 6D. Also there you should find about 2 volts. When this is all ok you can be sure that the cpu works fine, if not you'll have find your problem.( a missing signal is a short on the adress line somewhere , look carefully and if nessesairy cut some runs to find the short...bent the pin out of the socket ,and look if the signal is there, if so it is a short for shure, if not the cpu chip is broken.......) What else can be wrong.. only the selection of the pogram chip or the pia's, which we'll investigate now.

Chip selection

We're still working without program chip. Because all addresses will be addressed, every selection address of every PIA and eprom will be reached too. By using selection chips, these are chips 8D and 8E, the selection of a PIA or the Eprom ,is made by using 1 pin. This is pin 23 for the PIA's and pin 20 for the eprom (in 5C). Of course the selection is continued within the chips themselves, using lower addresses, but as we've already checked the address lines we're confident they work. This selection is done using the chips in 8E, 7E, 7C, and 8D. You see on the schematics at the output of 8D the PIA addresses (3400, 3000, 2C00, 2800 and 2400), these ones you find on pin 23 of each PIA. So on each pin 23 you should find about 4 volt and then you're sure the selection is ok. If not follow the selection- signal backwards until you find the problem. Same for the selection of the eprom on 5C, this can be found on pin 20. Tracing these signals back, is also limited, there are only 2 or 3 chips between address lines A14 and A15 and the final selection signal which comes out of 8D (and on out of 8E, address 2200).

One last case, if there's something wrong with one or more data-lines. If all the rest is ok then put the test-eprom back into 5C. The program will run but the PIA's won't react as no data arrives there. Data lines of chip 6802 pin 26 to pin 33 should move and have 2 to 3 volt. Check them after the buffer 5E, if one is missing then look for a short. Don't forget 6802 has already been replaced so his output should be ok, only a buffer can be broken or there's a short on the data line which shows the problem. Can easely be checked by bending the pin of the exit of the buffer up and checking if the signal does come out of this pin. If so then there is a short, if not the buffer is broken. If you have a short then you'll have to interrupt the data line and find which IC causes the short.(by cutting here and there some runs)A work which takes a lot of time, but this really is the worst case scenario.

Now we're finished and with this you've got about 95% chance that the important parts of your pin work and it will start.

Remark

Why not check the addresses and data lines when they arrive at the PIA's ? Well because there are 6 PIA's, the chance is very small that all of them get no addresses when we check them as ok when leaving the address buffers, same for the data buffers. The only doubt can be at the data and addresses which arrive in the Eprom at 5C. This one is in a socket and can have a bad connection. So do check this one..

Memory test.

When the first part of the test is finished we start the memory test.There is only one memory chip on the board in 5D.The Data East has no push button on the cpu board ( it is foreseen in the schematic...) so we have to launch the memory test manually by grounding for a very brief moment pin 6 of the cpu chip ( IC 3D) This will provoque a interrupt and starts of the memory test. When the test passes ok the flashing of the control led will continue, if the test finds the memory bad the flashing will end , and the test runs continously on the memory that allows us to check the signals arriving at the memory chip 5D. Signals that we have to find there are as follows:

Pin 1,2 and3 = 0 volt. Pins 4 to 19 = 1,5 to 3 volts. Pin 20 = 4 volts. Pin 21, 22 and 23 = 0 volt. Pins 24 to 28 = 3 to 4 volts . Measured with an universal voltmeter.

In most cases however the memory chip itself is broken.

Extra output tests.

In the new version 4 are included the PIA outputs CA1 and CB1, and an output command at address 2200 , a direct databus to Solenoid drivers command.. This way we will create outputs on all external drivers.

The CPU board includes the drivers for solenoids, display's, lamps and the output for the switch matrix. We can check these right to the output connectors. We are using the well know LED strip plugged in at the various connectors.

The LED strip;

A number of LED's every LED in series with a 470 ohm resitor, and the common to a red wire , that we will plug in the 5 volts. Plug in the connector at the CN that we have to check. If some outputs are missing use the schematics to follow the dancing signal from the PIA ( 6821) passing the drivers to the output connector .You can use a voltmeter or a logic probe.

Output switch matrix.

Coming out at CN8 , all 8 LED's should blink.

Sound drivers .

Coming out at CN21. The LED strip will show LED at pin 1 always "ON" , LED's at pin 2 to 10 blinking.

Display output.

Here we need a LED strip with another ( small) connector. Do not hesitate to make such one. He will serve you for different other boards. Bally lamp driver , Zaccaria CPU board , Atari boards and some others.

The LED strip with a smaller connector.

Outputs are on CN22, all the LED's will blink.The LED on pin 1 is always "on".

Solenoid outputs.

We find these at three connectors.

CN12 Output on all 8 pins.

CN11 Output on all 8 pins.

CN19 Output on 6 pins. ( 3,4,6,7,8,and 9)

Lamp drivers :

The lamp drivers show some differences, this because they are foreseen to work on a 18 volt tension that is not present , on this bench connection.

We find the lamp drivers at CN6 and CN7.

To compensate the missing 18 volts , we temporally connect pin 1 of CN4 to 5 volts. With the LED strip on CN6 we will see all LED's blink once. Switch the 5 volts on and off to see if indeed all 6 outputs are there.

Remove the temporally connection between CN4 pin 1 and 5 volts. Now plug in the LED strip at CN7. All LED's that will light up poorly will light up normally at the rythm of the test .

This ends the complete testing of the output driver circuitry.