4 slot audio problem from hell

WOW.

This one was a bitch to track down and repair.

Complaint: Board loses sound. Owner thought it was a cap problem.

Symptoms: Board plays test sounds OK. No startup music with cart installed. When playing Shock Troopers 2nd Squad the sounds during attract mode are missing and all sound dies when the siren was supposed to sound during the first boss battle.

Started chasing this down as a cap problem but with all the other audio working fine and the sound disappearing at a certain spot every time it was obvious it wasn't a cap issue.

Swapped out the YM2610, S1 ROM, Z80, and 6116 SRAM then tested. Swapped out the 74LS244 and 74LS245 chips at G/F1 and G/F2 then tested. Pulled out the 74AS245 chip at R2 and the 74AS244 chips at P1, R1, and R3. Tested them in a ChipMax programmer and found the 244 at R1 was bad. Reinstalled the other ICs, replaced the bad one, and the game fired up with all sounds.

Hope that helps someone fix their board. This one was a PITA that took a lot of time to troubleshoot. It's hard to use a logic probe on these chips since they are on the bottom board.

RJ

Awesome!! Great Info as always..Thanks for taking the time to explain the repair and post it..


..
I'd love to see what it looks like to remove/install one of the chips via video someday.

Yeah good info as usual RJ, keep it up.

Thanks guys!

I've been horribly busy with extra projects at work so I haven't been repairing many boards lately. There are a couple of members waiting patiently for me to finish up all this stuff at work.

It took me a long time to finish this one for a patient board member. Heck, I was in your 'hood last week druchri. Spent a week there for work, proctoring labs for a world wide gathering of security specialist SEs. Now I remember why it was so long since the last time I developed & proctored labs. It takes a sh*tload of work!

RJ

Hey come to my hood again and I'll put you to work on my 4-slot!

I know I'll be out there in April for sure.

RJ