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Bally SQUALK AND TALK sound board AS-2518-61

This is the most elaborated sound board in the Bally pinball's of the 80's. We can connect an extra " vocaliser" board , to extend the number of sound and phrases.

The board has a self test at power-up. On the board is a led , that will flash a number of times (5) to indicate wich elements are ok ( or not ok). NOTE: a brief flicker can occur at start up, this does NOT count as a flash.

The first flash means the memory is ok. That can be the internal memory portion of the CPU ( 6802) or the external memory chip ( 6810).

The second flash means the PIA at U7 is ok.

The third flash means the second PIA at U11 is ok.

The fourth flash means that the sound generator AY-3-8912 is ok

The fifth flash means the speech decoder TMS 5200 is ok.

Why would one use an extra test program, if there was a self test? Well, the self test indicates something is wrong but brings no solution (just replacement). The outputs of the PIA's are not tested. The most simple fault will stop the self test from running at all, where this extra test will run without a PIA or a memory chip on board. It still will perform the test! We also work around bad sound roms at the beginning of the test. We could test the PIAs and the memory chip by plugging these in the CPU board. This is a partial solution, but brings no answers if there was something wrong in a socket, a short between traces or an address or databus pulled low or high permanetly by another faulty element. So we choose for the extra test anyway. Let's look to the practical side of things...

The schematic of the board here

A very good explanation by Clive Jones about this board here

The test program first will test the CPU and circuitry, the PIAs and the memory. The memory can be an external memory type 6810 if we use a 6808 as CPU chip. In case we have a 6802 CPU the external memory is not needed, because the 6802 has a portion of internal ram that will be used instead. If these initial tests are done, we check the amplifier chip in a simple way and then, let the self test take over to determine the status of the sound generator and the speech decoder.

The squalk and talk board

Place the test eprom in the socket of Sound ROM U5. When tensions are applied the test will run immediatley. If ok, the connected control led will blink. If so you can measure the outputs of both PIA chips (U7 and U11) Pins 2 to 17 + 19 all will "dance" up and down between 0 and +5 volts. To start the memory test push the button on the soundboard, the control led will stop for a brief moment and then continue blinking. If the memory test fails, the led will stay steady "on" or "off", but testing continuosly in an endless loop, this allows us to measure the arriving signals on the memory chip.


All we need is a 12 volts supply, a -5 volt supply, a loudspeaker and the test eprom. Find the test eprom image here ( 2716 ) and here ( 2532). I made both images because boards are equipped with either one ot the other of these type roms.

Für alle, die keine Eproms brennen können oder wollen, gibt es fertige Eproms mit Leons Images hier im Shop

How about that. Well, on the board are a lot of jumpers, we do not change these but use a type of eprom that suits the board. The jumpers used to change or adapt for a 2716 or a 2532 are listed here . These are the ones we will not change, the others and their functions;

L = you have a 6808 processor and a 6810 memory chip on board.

K = You have a 6802 processor and no extra memory chip on board.

H = No vocaliser board.

J = With vocaliser board attached.

EE = No AY-3-8912 sound generator.

For the test purposes, always, N and DD jumpers present, and no CC or M jumper. This allows us to change the volume with the potentiometers on the board (most common setting).


To excecute the first test only connect +12 volts at J1. Pin 17 = +12 volts, pin 16 = ground.

Jump a wire between C14 and C15 both - sides.

Connect the control led to pin 15 of the CPU U1 and to ground.

Bottom in the middle the +12 at pin 17 and 16 of J1. The control led between pin 15 U1 and ground, and a temporally connection between C14 and C15 negative sides= ground

Control led

The control led is a normal led in serie with a 470 Ohm resistor, and used in many appliqations of this site , to make one look at the page ," Repair of Bally/Stern CPU boards." here the photo ..

Control led.


When tension is applied the test starts immediatley, the control LED starts blinking. We can check the outputs of both PIA's U7 and U11, their pins 2 to 17 + 19 will go up and down between 0 and +5 volts. If this is not the case, then we look at some basic signals at the CPU U1, to find out the reason why. On pins 2, 3, 4 and 40 we must have +5 volts, and clock signals at pins 37 and 39. At pin 37 the signal is strong 2,5 volts and at pin 39 at least 1.5 volts. When these tensions are ok and the clock is present the CPU should start, if not remove the test eprom, the memory chip U6, both PIA's U7 and U11, the TMS5200 and the other sound Roms U2, U3 and U4. Now look again if the CPU works. Check for signals at the address bus pins 9 to 25 (except pin 21 = ground). Signals should be between 0.5 and 2 volts, the same on the databus pins 26 to 33. Now we have two possibilities: signals are there = CPU ok , no signal(s), replace the CPU.

Now, we have the case of a CPU running fine in stand-alone but with the test eprom in place the test wont' work (control led does not blink).

We remove again the test eprom and look at the signals arriving on its socket. The different data and address signals are present? If not, bad contact in the socket, look at the selection signals, we need a 0.5 volts signal at pin 19 and a 4.5 volts signal at pin 20. Use a universal voltmeter, a digital test lamp or a scope to control these tensions and signals. Is there a missing signal refer to the schematic to see where it comes from. At first, always suspect sockets. If it is an address or databus signal that is missing, bend up the pin of the CPU where it came from. If now the bend up pin delivered the signal means you would have a short on that address or data line. You have to look that up. Normally you did find the fault. Place back the test eprom first. After the test works (control led blinks) place back the other chips. The test must keep working after these are put back, otherwise one of the chips is bad. Now check the PIA outputs. These will " dance" up and down from 0 to 5 volts. If some are missing the PIA is bad, if all are missing first check the socket connections. All the signals to the PIA including the selection signals are data or address bus signals. As these where already checked we have to find at the pins of the PIA's the same results. Additionally, check the pins 21 ( 4.5 volts using a 2532, 0 volts using a 2716 ) pin 23 - 4 volts , pin 25 - 2,5 volts. If missing some of these take out the schematic and look where the signal came from. There must be a cut or a bad element (easy). If the signals are all present, and still no outputs the PIA is bad. At this point you must have found the fault.

Memory test

We start the memory test by pressing the push button on the board. The control led will stop blinking and restart blinking after about two seconds if all was ok. If not ok the control LED will keep its current state, which can be a steady on or off. Anyway, the test continue checking the memory and allows us to measure the arriving signals at the memory chip U6. On pins 1, 14 and 15 we have ground, on pin 24 +5 volts. All other pins receive signals between 1.5 and 3 volts. If that is ok, and the test indicates a bad memory, you can be shure the chip is bad. Otherwise, again suspect the socket. At this point you must have found the fault in the board.

Amplifier, sound generator, speech processor chip's

To start we connect the -5 volts and the loudspeaker. The loudspeaker at pin 1+2 of J2, the -5 volts at TP4. We can remove the control LED.

We still need +12 volts on pin 17 and GND at pin 16 of J1. Keep the connection between C14 and C15. On top the -5 volts arriving at TP4 ( black wire) and the loudspeaker connected at J2 pins 1 and 2. To provide the +12 and the -5 volts use a power supply of a PC.

To test the amplifier, we inject some noise by putting our finger on different capacitors connecting the stages of the amplifier chain. Starting with C25, touching here will induce a loud humming sound, if not the TDA2002 U18 is bad. Checking the next stage we touch C24. If no humming IC14 is bad. Next is C19, if no humming here, U13 is bad. Another stage is C36, no humming again U14 tested now via another channel, and last one C35 another channel to test U13. If the amplifier stages are ok, we put all the original sound roms in place and launch the board again. Look at the 'on board' led; it should flash 5 times; The first three are for shure as they test the memory and the both PIA's who are certainly ok at this point. the 4the flash tells us the soundgenerator AY-3-8912 is ok and the last 5th flash means the speech processor TMS5200 is good. If the 4th or 5th flash were missing replace the sound generator or speech processor. If ok, push the button to launch all sounds of the board. When ever you have no flashes at all, replace the sound roms.

Last possibilities

If the board works ok on the bench and not in the machine, make sure you have -5 volts at TP4. The -5 volts is made from the 6.3 volts AC arriving at pins 7 and 10 of J1. Input at the 7905 stabilisator should be about -11 volts. If wrong, replace the diode and both capacitors, if ok and no output the 7905 is bad. Check also the connections and the loudspeaker of the machine.

Danke LEON - R.I.P