I am currently fixing a CPS2 A board here with a multitude of issues related to sound. I'll try to explain them the best I can, what I've tried so far, and what I plan to try soon. Just looking for any extra advice that may help, and hopefully turn this post into a repair log for anyone else with similar issues, because there's very little information on this combination of issues out there.
The JAMMA edge sound will only work if the speakers are plugged in after the CPS2 boots. However, at random there is no sound at all, and this typically lines up with the L channel of the RCA connector having no sound (makes sense as mono is driven off L channel). There will be static and crackling sometimes when this happens, but not all the time.
On the RCA side, the right channel has a lot of noise and is super quiet, but always works. On the left channel, it is perfect *sometimes*, but other times it will have no sound, with static and crackling, maybe 1 or 2 small fragments of sound coming through.
So far, I've tried replacing all the caps towards the L channel on the RCA connector, but that didn't change anything. Because the issues are intermittent, I also tried reflowing most of the components on the amp circuit with no luck. I also checked all the traces with a magnifying glass, didn't see any broken traces and the PCB looks new.
As far as what I plan to do, I want to try swapping the LM833 at UA10 with a new one and see if that changes anything. Once I get my good analog scope back (or some low-power wired headphones), I plan to follow along the circuit and see first where the R channel is dropping, then diagnose the weird stuff with the L channel / JAMMA edge. My bet for the L (and possibly R) side is bad caps somewhere on the amp circuitry, so if probing gets me nowhere I'll just recap the unit... which could also be the cause of the speakers working only if connected after boot?
But if that all fails, any ideas on what it might be? I was told to check the supercapacitor, but will that cause such odd issues?
Thanks in advance.
The JAMMA edge sound will only work if the speakers are plugged in after the CPS2 boots. However, at random there is no sound at all, and this typically lines up with the L channel of the RCA connector having no sound (makes sense as mono is driven off L channel). There will be static and crackling sometimes when this happens, but not all the time.
On the RCA side, the right channel has a lot of noise and is super quiet, but always works. On the left channel, it is perfect *sometimes*, but other times it will have no sound, with static and crackling, maybe 1 or 2 small fragments of sound coming through.
So far, I've tried replacing all the caps towards the L channel on the RCA connector, but that didn't change anything. Because the issues are intermittent, I also tried reflowing most of the components on the amp circuit with no luck. I also checked all the traces with a magnifying glass, didn't see any broken traces and the PCB looks new.
As far as what I plan to do, I want to try swapping the LM833 at UA10 with a new one and see if that changes anything. Once I get my good analog scope back (or some low-power wired headphones), I plan to follow along the circuit and see first where the R channel is dropping, then diagnose the weird stuff with the L channel / JAMMA edge. My bet for the L (and possibly R) side is bad caps somewhere on the amp circuitry, so if probing gets me nowhere I'll just recap the unit... which could also be the cause of the speakers working only if connected after boot?
But if that all fails, any ideas on what it might be? I was told to check the supercapacitor, but will that cause such odd issues?
Thanks in advance.
