Leon Borre Bally AID2 Test Board

Adapted AID2 test-bord for CPU Bally and Stern.

This board is made based on the known, but less seen (I've never seen one myself) AID2 test board which is described in the repair manual of Bally. I've added 5 extra's so it's easier to use and it's possible to run a more complete test on the selection-circuits of the rom/eprom chips. Further it's required that you have the schematics of the cpu-board and Ballys book " Bally Electronic pinball games repair procedures" module component replacement. Preferably edition F.O. 560 of1977....... which you can download here..............(link no longer available)

Of course you can use this board all the way like a 'normal' AID2 board, and not use my changes to the normal Bally manual.

How does it work..?

When you connect the HALT (stop) signal on cpu 6800 to ground (which is pin 2), something that never happens on a working pinball machine, this signal is forced by a resistor (R135- Bally and Stern) to 5volt. When this signal goes to 0volt the cpu stops working and it will make all it's outputs 'floating'..(high impedance) you can force them high ( 5) or low (0 volt) as you wish. This can be used to force address and data lines to high and low, and check them on all the points they are connected to. This means the path is ok and there is no short, or a wrong polarity exists because the chip is broken or has a short inside.

Description of the board.

The board is a piece of universal board on which I soldered a 34 pin connector which goes to J5 of the cpu board. There are 2 leds, 1 switch and 3 female jacks. The leds are connected to the blue jack, in which you put a test-wire. Touch the points you wish to check, and read the polarity: = high, red led, - = low, green led. With the switch you force ALL address, data and other signals to be all high or low, using the other jacks it's possible to force seperate signals high or low. With all these combinations you can check everything.. ...

The simple schematic..

Pins 1 to 23 33 connected via a 1,2Kohm resistor to common of the switch, which can be connected to or mass. Pin 24 (halt) via a 1,2Kohm resistor to ground. Pin 30 = 5volt and connected to the red jack. Pin 31 is ground, connected to the black jack. O and 5volts to the switch.Blue jack is the common point of the 2 leds. Because the red led is connected over the resistor to mass, it'll light when the blue jack gets 5, the green led is connected to 5 so will light when the blue jack is connected to ground. If nothing is connected to the blue jack, BOTH leds will light dim. An alternating signal will also light both leds (brigther as when there's no signal). Special is pin 26 (VMA), this is connected to a resistor but the other side of the resistor is not connected ! The purpose of this is to reach this pin (and VMA) and force it, which can also be done using TP7, but this test-point does not exist on a Stern cpu board -200 ! It does exist on Bally -17, -35 and Stern 100. To make the use of this AID2-board universal (also on Stern -200) I have added this resistor...

If you check the diagram with the AID2 in Bally's book (page 28) you will notice 5 changes....

1) I have added a resistor on pin 26 (VMA) and pin 33 (which is address line A14) TAKE CARE: not all boards have 34 pins on connector J5 ! Some have only 32, don't worry, align the AID1 print on the most RIGHT pin 1, if pin 33 and 34 are missing this means address A14 is not used in the chip-selection.

2) 2 leds with their plug have been added so it's not necessary anymore to test with a more heavy DMM...

3) The switch connects the common part of all resistors with or -, we don't use wires with alligator clips like Bally did.

4) There's a red jack to force a positive voltage on pin 26 VMA (therefore we need this extra resistor). The reason for this will be explained later..

5) As in the previous point, on the Halt-signal (pin 24) we can force a positive voltage. This way we can leave the AID2 board in place (connector J5). If we force 'halt' positive the AID2 will be disabled, but we can still use the tests-led on it....

How to create it:

You need: 1 universal print with 1 solder-island for each 3 holes, 28 resistors of 1,2kohm, 1 switch with 2 positions, 3 female jacks, 2 test wires, 2 leds (red and green), and a long connector strip (34 pins) of the type you make ic-sockets of......

The print is 9 x 4,5 cm and has 3 holes for each solder-island. 3 jacks of different colors: red, black and blue. Test wire made myself and is 20cm long, one side fits the jack, the other has a mini-hook so it's easy to pick up a small wire. You'll need 2 of those, they are needed to bring 5 or 0 volts to the resistors.

The construction with pictures...

Drill holes in the print, and solder the connector strip in place, this on the solder side.

CAREFUL: small error here, the right jack must be red...

Place the leds, connector and jacks. Beneath the switch I've put a print to make it clear which polarity goes from the connector to the common part of the resistors...

First place the resistors. They are all 1,2k ohm, but the 1 to 8 and 23rd are from another company, that's why they look different. The first 8 are data lines, the 23rd is the R/W line. All the others are the address lines. Therefor I made this difference, so it's easy to count. The resistor of the halt-line (pin 24) has been placed sideways and painted yellow, so it's different from the others, so you can clearly see if there's a 'force' wire connected to it or not.. if so, the AID2-tester does not work. Make the connections like on the schematic and you're ready....

The resistors are at one side attached with a long (1cm) lead which stands above the print, so it's easy to reach them with the measure-wire or the pin to force it to - or .

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Before you solder the red and green led it's best to do a test to check the polarity of the leds...

Solder a 1,2Kohm resistor to one of the legs of the red led. Bring 5 volt to the other end of the led, and ground to the free side of the resistor. If the led lights up, it's ok and can be soldered like that. The free side of the led to the blue jack and the free side of the resistor to ground.

If the led does not light, turn around the connection: solder the resistor to the other leg, test it again and now it should light....

For the GREEN LED, also solder a resistor to one of the legs. Attach mass to the free leg of the led, and 5 volt to the free end of the resistor. Again 2 possibilities: it lights, ok, attach like that: free side of led to blue jack and free side of the resistor to 5 volt. It doesn't light, solder resistor to other leg and try again.....

Also check the switch so the side is connected to the common of the switch if it's switched to ' ' as noted on the front, and minus is connector to common if it's switched to '-'......

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Placed on the cpu board,in the pinball, ready for use!

Manual.

The AID2 tester is used if there's nothing anymore which works, so when the led on the cpu board does not flash, stays on or is off completely. A second option to use this tester is when there's something wrong with ie U10 (4 led flashes), you replace U10 and the result is the same...(or another replacement that gives no result...)

There's a last problem if you're working on a Stern cpu board. Although Bally and Stern cpu's are technicallie, and in use the same , the numbering of certain (selection-)chips is different. If you take the Bally book as reference, you'll have to check with the cpu schematic of Bally and Stern to check if there's a reference to a chip, which number it has at Stern and which pin is input and output. It's a bit more complicated but you'll get used to it. One example is signal VUAO2 which is created by 4 logic ports which you'll find on both schematics between U9 and U10. For Bally these are U15d, U15c, U14d, and U19b. For Stern these are U15a, U15b, U18c, and U19b, still the logic is the same. So take care if the Bally manual has a reference to chips and connections !

If you think it's time to use the AID2 tester, plug it in on J5 of the cpu board, but let the halt-signal high by forcing the resistance of pin 24 to (red jack). This way the AID2 board is in place, but not working..we can use the "Test flow-chart " on page 27 of the Bally book, and at the same time we can use our test-leds to check what the flow-chart indicates....

For a start they'll let you check at symtom 1A (page 29) the voltages, which is obvious if the led does not light, that you'll check which power is available. Then we're going to our example: the led stays on. Symtom 1C, follow the flow-chart, measure the clocks on pin 3 and 36 by using the test-pin of your leds ( plugged into the blue jack) and touch both pins. As the clock signals are symmetric, both leds should light each as strong as the other. If one of them doesn't light then you've found a problem. Same for the signals on U16 pins 4, 5 and 10 as on the flow-chart. Follow the flow-chart further until page 30. The reset-line can be checked with the leds, the red led has to light on pin 40. Same for halt-line, red led should light (pin 2), the flow brings us to VMA (pin 5) both leds should light at the same time. Then you've got on the flow-chart E) error in VUA-O2 circuit........ this is the circuit between U9 and U10, 4 logic ports which make signal VUA-O2..... VUA-O2 comes from the output of the last port, you'll find both seperate signals VUA and O2 at the entry of the port before that. O2 is an alternating symmetric signal so both leds should light, also VUA is alternating. The composite is alternating.(both leds light) Is it ok then we'll continue, otherwise you find out which signal is missing and why... VUA or O2.

Then we end up on page 30 symtom IIA.

If you still haven't found your problem after the short IIA procedure you'll end up at A4-II Bus associated failure procedure... here you'll need all possibilities of the AID2 tester. Take off the positive force from the halt-resister, so the AID tester is working, and set te switch at - (number 2 page 31) Test with the leds (number 3) and everything should light up green....

On number 5 (page 31) switch back to , and as said in number 6, check all resistors and everywhere you should light the red led. Continue to 8 and 9 where you'll connect each resistor one by one with - or ground and measure all other not connected resistors to check if they still light up the red led. This way you'll check for shorts between adjactent lines......

The connector points or the resistors which are connected to them, have access to : (starting on the right side) 1 to 8: data lines D7 to D0, addres lines A13 to A0 on pins 9 to 22, and A14 is at the end on pin 33.

Now we're on number 10A on page 31. There are no force wires anymore and we'll test with the leds, everything should be red.

On number 10 B C D E of page 31, it's better NOT to use Bally book ! They let you test the selection of U1 to U6, but this is not the same on all models of cpu boards and can be different if you are using roms or eproms, and might be dependent on certain straps. The universal way to proceed is this: On U1 to U6, test pins 1 to 11, 13 to 17, 22, 23 and 24, they should all be (red led). Then there's still the selection inputs pin 18, 19, 20 and 21, which can be different. Check your manual and your board and where the jumpers are, and check with the led-tester what arrives. I'll give some examples. Bally -35 with eproms in U2 and U6: on pin 19 is address A10 because all address lines are forced to so you'll have to find red ( ). Now a difficult one: pin 20 of U2 is connected to E11 which has a jumper to E10, where you'll have U17b with 2 inputs.. VUA-O2-A12 on the one and the reversed signal A11 on the other..... This means we'll have to force A11 (resistor 11) to -, and bring to live VUA-O2-A12... This combined signal has 02( present), also A12 by AID2 forced high..(present) only VUA is missing.. Therefor we'll force VMA to (resistor 26) and now the selection signal on pin 20 will be high (red) which means the selection works. (if not you have found a problem). This way it is necessary to check all possible chip-selection signals. Check( using the schematic) what should arrive on a certain selection pin, force the signals so they are ok for this selection and check if you find this on the pin. This is possibel because you can bring to live VMA even if the cpu has been blocked by AID2.( This is what you do using TP7 and TP1 in the Bally manual) If in the selection there's a signal with a - line above it, this means it is a reversed signal which you can force using - (negative).

Now we're already on page 33 symtom A4-III, number 9 also uses TP7, you should force positive on VMA (resistor 26) and you find on U7 pin 13 an alternating signal (both leds).

Symtom A4-IV has no problems, then there's number 9 which refers to a table, A4-1. Remember that Stern -200 also has U13 apart from U8, which is identical for selection, only data signals are different. U8 has D0, D1 D2 and D3. U13 has D4, D5, D6 and D7. The polarity of both sets are also the same.( all data D0 to D7 are forced the same way by the switch)

Symtom A4-V and A4-VI is no problem, instead of connecting TP7 with TP1, you'll force VMA (resistor 26) with . (The 1,8V which you should get on pin 25 is in reality an alternating signal).

The rest of the book can be used without problems.

I return to the case of which you have 2 or more flashes. When you replace the component and still have the same problem.. Most of the time it will be a bad contact in the chip socket, or a bad selection, as I already gave some examples; you'll have to check with the schematic the selection-pins ( R/W ..E.. CS .. VCC2 and VUA-O2-A12 are the notation for selection signals) force the selection signal and check its arrival on the pin. Address lines A0 to A14 are equally important but can easyly be checked by starting AID2 and testing on and -. Look out for signals which are compositions of other signals. Some selection-signals should be and others which should be -. CS is positive, CS with a line above means negative. I wish you a lot of patience and luck....

I know this method (AID2) is elaborated and needs a good concentration, but it's guaranteed you'll find almost every problem possible with a cpu board.. Certainly in case you have a bad socket somewhere, and the difficult cases where one of the chip-select ports is broken.....