I'm hoping for a bit of help with my Bally Squawk and Talk Board after a careless mistake has created more work for myself.

While investigating other issues I was having with my Fathom I took it upon myself to check test points on all the boards in the backbox. My Sq/T appeared to boot up fine with the appropriate amount of LED flashes and I was reading proper test point voltages across the board. Before I could leave well enough alone my positive meter terminal grazed the exposed male header pins next to the main connector and caused the game to reset (just to the left of the big capacitor).

Since then my board will not boot -- it displays the initial flicker, a normal first and second LED flash, then produces a third LED flash of longer than usual duration (with no further flashes).

When checking test points now I have the .8V at TP4 (had -5V previously), have nothing at TP9 and TP11 (had 1.2V previously and 1V Previously, respectively), and have 2.8V at TP5 (had 0 previously). Other test points have been the same: TP1 - G / TP2 - 5V / TP3 - 15V / TP6 - 2.6V / TP7 - 0 / TP8 - 2.5V / TP9 - 0 / TP10 - 3V / TP 12 - 5V

After reading thru some of the archives and Pinwiki as best I could understand I swapped out U11 with a good 6821 chip to see no difference. I've examined the board as best I can and see no burnt resistors, scorch marks, etc. (plus there is no burnt smell).

All caps had previously been replaced. As I sit here and think about the situation I did not go back and look at the connector to see if any of the wires there were compromised, but can do that tomorrow. All General Illumination is on/lit.

Edit - forgot to mention that I can hear some "sound" from the speaker when I adjust volume(s) on the board, but no game sounds are created.

I was not able to find any information on the longer than usual third LED flash -- any help or suggestions are appreciated. I've since resolved the other issue I was having with the game (located in the coin door!), now everything is up and working. . . except the sound.

Pictures front/back of the board attached.
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Thank you for the replies so far. I was called into work for a bit after my first post but will now try to give the schematics a good look. I have GI -- will confirm that everything is being delivered to the sound board connector as intended.

Thought about the regulator -- just not as easy to swap one of those out as a chip.

I should probably stop swapping things at this point and try to read the schematics anyway. . .

No doubt you know more about such things than I do.

What I do see from the schematic is the voltages of the three exposed pins to the right of the connector -- 16, 17, and 18. If I'm reading correctly 17 is 12V unregulated in, 16 is unregulated return, and 18 is tied in with the GI BUS. . . if I touched 12V to the GI BUS by connecting 16 or 17 to 18 could that be enough to fail the regulator?

You are right -- I'll check tomorrow and report back.

Zoomed in on CR7 and CR8 (bottom right) -- probably cannot tell a bad diode from the picture. Thanks again for the help this evening!

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I think its just a shadow.

Worked late today, but stopped in on the way home and here are my findings.

Pin 7 has correct incoming 6.3 A/C. A trace connects pin 7 with the + end of C37 -- reading on the "leg" of C37 provides the same 6.3 A/C. By continuing to follow the traces on the back of the board the negative end of C37 connects with the left side of CR8 -- No voltage AC or DC is detected from the negative leg/side of C37 (not sure if this should be the case? Other Caps have a zero reading on the negative end but they are usually grounded), or at either end of CR8, CR7, or the regulator itself.

Looking at the traces negative end of C37 leads to the left side of CR8, then down to right side of CR7. Right side of CR8 leads to positive side of C38 and eventually down to the unregulated return at connector pins 15/16. Left side of CR7 leads up to C47 then eventually to the 7905 regulator.

Anyway, I seem to lose the ability to find a reading after C37/CR8. Bad capacitor? Bad Diode(s)? I suppose the diodes would be easy to replace -- they appear to be the common 1N4004 that I've used everywhere else on the game.

Hoping I can find those numbers tomorrow.

Diode test first, but I'm suspicious of the capacitor as there was nothing "leaving" the cap or at any point further down the line.

Either way I have some spares of both so with any luck there may be sound in the future -- I'll be sure to post back the results.

Thanks again for the help and guidance. I'm more of a hands on/see what I'm working with kind of guy and need a little more time when it comes to understanding the electronic workings.

The caps are 50V / 330uF as you mention -- to my simple way of thinking the extra 12V might not be enough to blow a 50V cap? Would I have heard a pop or smelled burnt electrics as well? Is it typical in this case to have no reading AC or DC on the negative leg of the C37 capacitor and at the diode further up the trace?

Sorry for all the questions. . . I like to know how things work.

Edit -- Or in this case, how things break!

Did just that today. . .

Started with CR7 and the voltage drop seems correct at 0.6V

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Checking CR8 -- what do you know, all zeros -- looks like this could be the problem.

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New 1N4004 diode in place. . .

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It worked! After adjusting some of the game controls I have both speech and sound! Thinking I will section up an old connector housing to cover those three exposed pins.

Many, many thanks to Quench and jj44114 for the suggestions and help. It was just a simple diode replacement, but I like to know why it needed replaced (beyond the fact that cooked it!).

Waiting on a few more parts to complete the playfield population -- a quick picture of how things are coming together.

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