My buddy picked up a Starship Troopers pretty cheap, but there’s no sound. Pinball with no sound = no fun. I figured I could help him get it fixed remotely, but that didn’t work out. I finally got a chance to look at the machine with him earlier this week, and we were not able to find the problem. I had access to an oscilloscope and we were able to dig pretty deep, but my knowledge of the circuit is not that clear, so we could only go so far.
Here’s what we know:
- AOR and AOL are dead, so there is nothing coming out of the LM833s going to the amps. I would suspect that the amps themselves are probably good.
- There’s no data coming into the TDA1543 via the 74LS74. The WS on the 1543 is not toggling.
- At one point, the signals on the data lines for this part of the circuit were very odd looking, never going above about 1.5V. Now, the last time I looked at them, there was just nothing on them.
- I found that the /RESET on the BSMT was low, and thinking that’s keeping the BSMT from running. Is this correct, and anyone have any suggestions for this?
- The 6809 is not in a reset mode, and appears to be running. Interesting how the data bus for this appears to be completely different than the data bus for the BSMT
- I’ve checked the other test points (6Mhz, Q, E, 24Mhz) and they all look good, though I only had one scope probe, so couldn’t verify the phasing between the Q & E
- I’ve swapped the main and sound 6809s, and no change, so I’d say both of those chips are good
- I’ve swapped the BSMT with a known good one from a Lethal Weapon, and the LW still works, so I’d say both of these are good, too.
One thing we don’t know is that we have not tested the sound ROMs. Will definitely need to look into that.

Anyone have any suggestions on what to look at next? Unfortunately, I no longer have “hands on” access to this machine, so anything we try will need to be remotely or wait until my next visit.

Thanks,
Jeff

Friday bump.
Yeah, I know I didn't make it easy...

OK, a little update, for those that are interested:
Over the weekend, I was by the machine again. I replaced all the sound ROMs. Still no sound.
I looked at the chips that interface between the sound CPU and the BSMT (74LS374, I believe), replaced and socketed them. Still no sound.
At this point, I think I've at least re-seated all the socketed chips in the sound section of that board. Still nothing.

So a question is, if I were to remove the board from the machine, could I put it on the bench, power it up, and hook up a test speaker to the output to see if I can track down the problem? Or am I better leaving it in the machine (knowing that the machine is over 2 hours away, and I don't have access to all my test equipment when I go to visit)? Will it work on a bench by itself?

Thanks,
Jeff