Kung Fu master no sound

Motoman202

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So the sound went out on my KFM. I started poking around and I'm a bit stuck. First thing I did was swap out the 2 AY sound chips with known good ones because that was super easy to try, No change. Then I started checking the 6803 sound cpu. Reset is good, I have clock on pin 40 but I'm not sure what I should expect to see on pins 2 & 3. It looks like it goes out and through the crystal and then back into the 6803? This is also the first cpu I have seen that has P lines. I know address and data lines but haven't seen P lines yet. I have activity on IRQ & NMI but R/W is static so that tells me it's not executing code. What really gets my attention is pins 8 & 10 of the cpu are floating. They come out of the AY sound chips at pins 29 & 27 but there is also a 74ls368 that ties into them. All connections are floating between the 3 chips. Pins 13 & 11 of the 368 are floating and pin 15 is high. I pulled the 368 and it tests good in my tester but I also swapped it out since I had it out and no change. Not sure where to go next.

20250111_164057.jpg
 
Strongly leaning into a bad 6803 cpu. Not a common CPU for me so I'll have to order one.
 
I don't have an answer for you but, for audio troubleshooting, I usually work my way from the edge connector audio pins, then the analog section (op amps, capacitors), then the digital section. Essentially follow the audio path back to the source. Check audio ROMs of course.

An audio probe is very handy for the analog section, you may have issues there that can be easily addressed.

Just sayin'…

p
 
I don't have an answer for you but, for audio troubleshooting, I usually work my way from the edge connector audio pins, then the analog section (op amps, capacitors), then the digital section. Essentially follow the audio path back to the source. Check audio ROMs of course.

An audio probe is very handy for the analog section, you may have issues there that can be easily addressed.

Just sayin'…

p
Thanks for the tip. I can't find an audio signal anywhere on this board.
 
Finally got back to this. Pulled roms to verify and now sound is working. So reseating roms seems to have fixed this issue.
 
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