Roland JX8P - Hearing other waveforms when both DCO's turned off on mixer

Just wondering if someone has experienced the below. My JX8P is having an issue when both DCO’s are off (mixer volume turned down to 00 within the parameters), I can still hear some of the waveforms when I press any keys on the keyboard (at a low volume level though).

I prodominantly hear the “noise” waveform and the sine one, but if I listen closely I can hear all of them mixed.

At first I thought it was my PG800 that had bad slide pots that wouldn’t go all the way down to 00 but if I check the JX’s parameter section, both DCO’s are off.

Just checking to see if anyone has any pointers as to what I could check? Or perhaps this is normal (though I never noticed it before)?


Sounds like early failure of the filtering capacitors. When these fail noise and other harmonics become noticeable. What your looking at is a capacitor replacement. You can pick away one at a time or just have them all replaced at once. But once, cry one is the cheapest route.

Depending on the tech you take it too, they may find something else, like failed tantalum capacitors. As said if you just pick away at it on capacitor at a time, it will cost you more in the long run. But see what the tech says first.

Thanks for the suggestion. You’re referring to the electrolytic capacitors correct?
If it were you, would you be looking at recapping just the power supply board, or main board (or both)?

I am not very good at troubleshooting these type of issues on vintage synths but I am very familiar with performing this sort of work so I was hoping to tackle the problem myself.

Is it possible that you had the resonance turned up high enough that it went into self oscillation? You would hear that even if DCO1 and 2 volumes are at zero. My jx10 does this.

Thanks but unfortunately that isn’t the case. Even with resonance and DCO1 & 2 volumes at 0, I can hear all waveforms when I press any key.

I started troubleshooting starting at the power supply first, and found an issue with the M5230L IC, and recapped the power supply (see topic The issue was still present so I decided to replace all capacitors on the main board, and the issue is still present.

Unfortunately this is the limit of my troubleshooting capabilities. It must be a bit of an unusual issue as I cannot find any information about similar issues online.