If subbing with a trim pot, I would use a 100K resistor in series with a 50K trim pot. That should give you enough variance around the original 130K without going too far out of range of the oscillator. It could actually be the value of C51 that has drifted out of spec as it is only 10 pfd.

My spare, dusty board is a -61a and it also has an empty socket at U10 (just noticed that yesterday!). I just ordered a couple off ebay to populate my spare board.

There are three sources for sound on the S&T. One is through the AY-3-8912 Programmable Sound Generator (PSG), This where simple tone and white noise related sounds as well as music can be produced (Think Early 80's Video Games). The TMS5200 for speech. And the DAC for complex noises/SFX.

FWIW, the board was from a Flash Gordon and the Date code on the TMS5200 is 8048. I have not tested the board yet (waiting for the AD558).

But I am thinking he installed a 500K trim pot and turned it down quite a bit.

I am having a hard time understanding the 240K (early run) vs 130K (later run) aspect. It makes me think they really had to tune the boards to various batches of TI chips. I know we noticed subtle differences from game to game when they were brand new but never anything too far out of pitch, I seem to recall it being mentioned on RGP years ago that the chips currently on the market could be rejects that failed to meet TI's specs at the time. So, before discarding a newly purchased 5200 that seems dead, I would certainly try the trim pot thing to see if it will respond to other R9 values.

I fired up my spare FG S&T in my Centaur this morning. With the 8048 date code and 130K R9, it sounded just like Flash should. I just couldn't tell if there were sounds missing (still missing the AD558) by just batting the ball around a bit.

Is it documented anywhere if the 240K matches up with a particular title? My FG S&T uses the 130K as do my Centaur and Eight Ball Deluxe.

I suppose that is possible . However, my Spare S&T is a -61a and has an original EFG serial number sticker on it so I can't be sure about R9 on a straight -61 ( I can't find any reference to it on the net).

I wonder where games like Midnight Marauders (Midway Gun Game), and Discs of Tron fell in the R&D sequence for use of S&T sound? And the YouTube videos show MM stole a lot of sounds from Space Invaders Pin.