New Information

New information on the quest to fix the sound problems on the Star Trip.

According to this info,

the SSU-1 is driven by transistors on the solenoid board (SDU-1) where the MPU board selects which sounds to play, triggers the appropriate driver transistor on the SDU which in turn selects the sound to be played on the sound board. Sounds are tested during the solenoid test where each of the four sounds should be played once for each respective solenoid transistor. The other SSU boards are driven directly from the MPU board, freeing up solenoid transistors for other game functions. For SSU-1, each of the four sounds is triggered by one of four transistors on the SDU, specifically, Q3, Q10, Q12, Q13. These are connected from J2 on the SDU, to the 8 pin pigtail that hangs off the SSU-1. The pin mappings are as follows:SDU J2 Pin -> SSU-1 pigtail Pin

2 (Q10, Red-Vio wire) -> 2

5 (Q12, Yel-Green wire) -> 5

6 (Q3, Brn-Blu wire) -> 3

7 (Q13, Grn-Blk wire) -> 4

Which means I have been looking at the wrong board, I've been looking at the main processor board when I should be looking at the Solenoid board. This makes sense as I have had to replace several transistors on the SDU already, looks like I may have another bad one!

This is good news and gives me hope for a real fix!

More work on the Star Trip sound problem

I spent some time tonight looking into the sound problems on the Star Trip table. The issue is that everything works fine for about 3 minutes then a whine begins and never ends. The sound effects try to play but the whine is loud and overwhelms everything.

After reading about some different ideas, I started by reheating all the solder joints on the main board. Not everything, but the ones that looked suspect:

Following that, after reading about problems with "Scanbe" sockets, I pulled the chips off the main board one by one and verified I did not have Scanbe sockets:

After putting it all back together - the same problem. Runs fine, works perfectly but the whine is teeth-rattling after a couple of minutes!

Since the problem occurs only after a few minutes, I reasoned it has to be either a capacitor or some connection that fails as it heats up...note to self, as I write this it occurs to me it could be a chip that fails as it heats up as well.

The next step was to see what board the problem was on: MPU (Main Processor Board) or MSU (Main Sound Unit)

While the game was on, I very carefully opened it up, hoping not to have another self-created disaster. Then unplugged the sound board. My reasoning is that if it is heat-related, unplugging the sound board and letting it cool while the main processor is working will tell me.

My assumption: after 5 minutes, when I plug the sound board back in:

1. If the sound continues, the problem is in the main board
2. If the sound is not there but comes back after a couple of minutes, then it was in the cooled down sound board.

After several minutes, I plugged the sound board back in and the whine was still there. It appears the problem is somewhere in the Main Processor Unit...sigh

Next step is to try and decipher the schematics enough to figure out where the sound-related components are and really dig into them.