I'm working on a 1980 Bally Rolling Stones with no sound. There was a AS-2518-32 sound board in there that "works" but the sounds are obviously all wrong as this game is supposed to have a -51. So I acquired a non-working -51 board and have attempted to shotgun repair it. I hate that approach, but I'm not as familiar with this board as I am with all the other Bally/Stern boards, so I've had to do things a bit less technically than I would like.

Anyway, I have no sound aside from the normal speaker hum that changes along with the volume pot. When I got the board it wasn't even doing that so I installed a new TDA2002 and now it's giving me at least "something" but I still have no game sounds. All test points read spot on except for tp4 and tp6 which read 0vdc at all times, but they should read 2.5vdc and .35vdc when sound is playing and 0 when no sound is playing.

Here's what I've done so far:
- reflowed headers
- replaced all caps
- replaced the AY-3-8910 at U1
- replaced the PIA 6821 at U2
- replaced the 6808 processor at U3
- replaced the 6810 RAM at U10
- replaced the ROM with a new 2716 at U4
- replaced the volume pot
- replaced the TDA2002 at U9
- replaced the crystal
- replaced the reset switch
- Checked for continuity from the top of each pin on every socketed chips to the bottom of the board.
- Q1 tests good, but I have not replaced it
- I have not replaced the non-socketed chips, but I certainly can.

Looking for some guidance here. The speaker hum gets louder and quieter with the volume pot and the hum "changes" in the normal kind of way when the displays change between HSTD and the last game score. (If you're used to Bally's from this vintage, you'll know what I mean.)

All of the address and data lines of the processor seem to be showing no life (under .1 volts) when sound should be heard. Can someone walk me through how to make sure the processor is running?

Any help would be appreciated.

Thanks,
Corey

Also, there is a serious lack of troubleshooting info on these boards on-line. I wish there was something like this available for the -51:
http://www.pinball4you.ch/okaegi/rep_soundold.html

I've used that link to repair -32 boards several times, but nothing similar exists for the -51. I would write something up, but I'm not that smart.

The -32 that was in there does produce sounds, so I'm assuming that the input lines are doing their job.

It's running an Alltek. I will try another MPU tonight, but I'm guessing the issue isn't on the MPU. I haven't yet ruled out an issue between the MPU and the sound board, though. Going to do that tonight. If I had another game to test this sound board in, it would really help. I know A LOT of people with pinball machines locally, but none with a game that uses the AS-2518-51.