Naomi 1 volume problem

[shess]

I haven't turned my Naomi on in a while and when I did I got no sound. I found that if I turned it (Capcom IO) up to about max, I can barely hear the game playing. I ruled out the amp because my CPS2 outputs nice and clear when hooked up to it. I connected a regular audio source on the input side of the IO and when going through the amp, the music sounds fine. So that leaves me with the motherboard. Since the sound is coming out, it sounds like either the caps or filter board are the problem. But since the audio section is just line-out, would the caps have much effect there?

 

[shess]

If anyone runs into this problem in the future, I managed to fix it. I got the cap kit from console5 which was like 98% correct. There are supposed to be 3x 470uF caps and on mine they were replaced with 220 uF. I tried to put the 470uF caps in their place and they were physically too big to put next to each other. I used some radial 470uF caps I had in my supply instead. Since I didn't know which section controlled the sound, I replaced the caps in sections by their cap value. After each grouping I tested the system to see if there were improvements. I had replaced all of the caps leaving the 10uF grouping (the largest) till the end. Nothing had made any difference up to that point. After replacing all the 10uF caps, the sound finally came through clear and loud. It was probably a combination of 10uF and others but I still have no idea where the sound section is. But at least now it's fixed.

I did email Ken at irepairsega and he said sound problems on the Naomi mobo are super rare. Usually it's the amplifier or cart with the problem.