Roland JP-8080, sound changes over time, stereo unbalanced

Synth Repair
1

Hi all,

hope you’re doing well. I’ve got a JP-8080 imported from Japan and it has 2 problems, possibly related to being out of use for some time:

  • the sound of a patch changes over time. I get the impression it goes higher up in pitch, like some filter is applied.
  • the stereo image is incorrect: left is louder than right by about 30%.

Could these be potentiometers needing to be cleaned? Or leaking capacitors?

Cheers!

BC

2

Running test mode (see page 9 of the service manual) might help identifying some of the issues.

For the first problem run the A/D test (5) and check if any sliders or knobs register any movements even though you’re not touching them. As you say that it happens over time, keep the test running for a while. If ghost movements are registered, cleaning (or worst-case, replacing) the affected pots and sliders might be able to fix the issue.

The sound test (7) might also be help with verifying the stereo balance issue. Double-check whether the stereo balance issue also exists with both L/R output jacks and the headphone output jack. If you are feeding the output into a mixer that has individual per-channel +4dBu/-10dBV settings, also make sure that both channels use the same setting, just to rule out that the problem isn’t in the JP-8080 itself.

1 Like
3

Cheers Johannes, did not know about that test, will attack this in the weekend because it’s annoying. As it happens over time, I’m suspecting something related to heat in some way. Or maybe not, because if I change patches to one down and back up, the problem is temporarily fixed as well. What could be the reason for that?

BC

4

Yeah, heat is unlikely as it’s a fully digital synth and there’s no oscillators to “heat up” like with analog synths - a heat issue would typically result in different issues such as unstable operation.

Here’s one more obvious thing to check. Well, maybe not that obvious until it happened to you once. A while ago I loaded some patches into a synth and they exhibited a similar behaviour - pitch as constantly going up while holding the keys. And it turns out, for whatever reason this is exactly how the patches were programmed. I’d suggest that you do a full reset to factory settings (which you can do through the same test menu) so that the synth is in a known state. Even if the patches were not programmed like that intentionally, it could still be the case that there was maybe some memory corruption while the synth was stored away, and a full reset should fix that.

5

Hi Johannes,
I did a factory reset before, which did not help. So I will look into your previous reply and do some testing.

Cheers and have a good one,

BC