Sorry to resurrect an old thread.

I've just got a box of Bally boards to play with and I have 3 sound boards 2 x -32 and 1 x -50 - all missing a random variety of ICs.

I've managed to source U10, U9, and U5

I'm having trouble finding U11 which is missing on the -50 and is an M86L93 on the other boards

I'm also missing U3 from 2 of the boards. for the games I want to use these boards in I would need E-729-18. I imagine it is impossible to find this chip and that an eprom has to be used. Just wondering if anyone can help me out here?

I saw on a previous thread that you used to make adapters for EPROMs to go on these boards. Do you still make them?

I think I’ll try and make an adapter for a 2716 using sone sockets. Which pins need to be shifted?

I’m making progress, but am now a bit stuck. I have 2 -50 soundboards that are making zero sound, not even a hum when I put them into my 6mdm.

I have verified that every ic is working by testing them in a working -32 board.I’ve also replaced the big caps on the boards. I’ve double checked to make sure I’ve not done something stupid like a backwards cap etc.

I’ve studied the schematic to look for the suspect component but I just can’t work out.

The -32 works fine in the machine so the speaker/wire/connectors aren’t the issue, it’s definitely the boards, it’s just odd weird that they are both -50s with the same issue. that refuse to make any sound. The jumpers also look to be correct.

Phot below of one of them.

341C3213-D4BB-4270-8211-B7F6F2739AF6 (resized).jpeg

C1B5EF25-156E-427F-B3C1-8EB69193D8B3 (resized).jpeg

Thanks @quench, I'll put the LM380 back onto the board - I just socketed them so I could swap them into a known working board to test each IC out.

I can confirm every IC in the board is OK because I have 1 by 1 swapped them into a working board. So now I'm looking for other causes - broken traces, shorted caps (i've replaced most of the electrolytic caps).

I'll try the screwdriver trick you suggested and report back.

No buzzing when touching any of the pins.

I am getting 6v at pin 2 and 3 of u9

From reading one of your earlier posts. I checked U9 pin 2 and I have 6v there. You said in the post that if there was 6v at pin 2 it’s upstream from there.

Any usual suspects? Where should I go looking now?

Do you know which resistor?

I have normal voltages at the test points.

All chips work - i have swapped them into a working board to confirm, so it must be another component, I just can't find it!

I have a second board which is making white noise to the speaker, but has 4.2v at pin 2 of u9. Similar story - all chips have been swapped out and checked in a working board, so it's not a chip issue. I've also checked the sockets for solder bridges and chescked traces. I am trying to work out why the voltages at pin 2 U9 are high, but following the schematic I find a bit tricky to work out what the voltage is supposed to be at each component.