Game: Flash Gordon (this may not matter)

Symptom: With this particular SDB is installed one wrong sound is played when certain switches are triggered. Also the background sound will not restart at times.

Analysis: The game behaves fine when tested with four other SDBs I have on hand. It only misbehaves with this particular SDB.

My first thoughts were this is a data issue so I approached it that way. I initially suspected the 74L156 but it is fine. Finally after a lot of head banging and misdiagnosis I booted the game with ONLY J3 attached. J4 is not connected, so no data that is being passed from the MPU to the SDB to the sound board should be affected, but it still misbehaves as described above (wrong sound, no background sound at times). But if I hook up one of the four other SDB with only J3 attached the game acts fine.

Any help is greatly appreciated!

The same behavior as described in the symptom of the above post, one wrong sound is played when certain switches are triggered. Also the background sound will not restart at times.

Yes, and on all the other SDBs I'm using to test.

Also, I replaced the .100 header pins as I thought maybe the issues were due to J4 not getting reliable contact. But nothing changed after replacing both J3 and J4.

Bump to see if anyone has any ideas.

Yes, S&T.

Nothing on SDB J3 Pin 7.

SDB J3 Pin 5 does go to Pin 9 on the S&T. I don't even see this referenced on the schematics for the S&T so I'm guessing it isn't necessary and I could remove it and then test.

I mean the S&T schematic, my FG manual has the S&T. It does not show 43v coming in on J1 Pin 9 from the SDB or rectifier board. Unless I'm missing it.

Sounds plus schematics show it coming in on Pin 9 but unused.

I'll try lifting it tomorrow and see if anything changes. Can't imagine it would cause any problems but at this point I don't have any better ideas.

Looked at the S&T, J3 Pin 9 is not connected to anything. So I don't see how this SDB can be causing the behavior it is.

I don't give up easy but I'm putting this one on the shelf as I need to fold up the game and move on to other things. If I get a chance I'll try it in another game and see if it misbehaves. Thanks for all the help.