Hello, I have a JP-8000 that’s been quite a headache and I’m at the end of my expertise with attempting to repair. I’ve replaced all of the capacitors on the board as they were all leaking and repaired a trace, but I have multiple dead voices. If I press the keys a bunch then sometimes I get a note out of it. When I do the sound test in the built in self test, none of the waveforms produce any sound except the “8 voices”, where I only hear the last two voices, and a clicking sound for the first 6 voices. Does anyone have any idea what this could be? Is it a dead/multiple dead DSPs? A faulty muting circuit? At least an idea of what I should check next? This is my dream synthesizer and it’s torn me apart that it hasn’t worked since I’ve gotten it
Hi, I have had the exact same problem with my JP-8000. I’m wondering if this is the same synth since I bought mine used in Austin around August/September.
The symptoms:
- 8 voice test: A thump/pop on the first six notes played and the two final notes sound normal
- The unit was originally resetting after roughly 45 seconds because the 5v regulator was overheating. It didn’t have contact with the PSU chassis, so it wasn’t dissipating heat. I fashioned a stand-in aluminum plate that resolved this problem.
- If the keyboard is played in split mode, the left half of the keys always produce a pop/thump. The right half intermittently plays notes.
- The A/D test produces audible tones when turning and sliding potentiometers. The tones change pitch and waveform (sounds like a triangle in one position and a square in another position)
Troubleshooting:
- I’ve confirmed it’s not the muting circuit as the issue is happening further upstream in the digital section. I measured the voltage of the muting circuit and wasn’t able to see any fluctuation during the pop/thump or empty notes.
- Validated on a scope to the best of my ability that none of the transfer paths between the four DSP chips are sending dodgy voltages.
It’s been about a month since I took a break from this because I wasn’t getting anywhere. I’m not skilled enough with a scope or logic analyzer to determine where the fault is. I can confirm though that the CPU works well enough to send/receive MIDI on all controls. I’m considering just repurposing this as a midi controller for another DIY synth project until I can get a replacement main board assembly. Or until someone can help me further troubleshoot. I’m on the waitlist at Synthaur for a new main board. Who knows when that will come about though.
In case it’s helpful to anyone, I’ve documented a lot of my efforts in this Reddit thread:
Hello hodelo. Not the same synth, I bought this one from Japan a few years ago and I still have it. I’m suspecting at this point there’s a broken trace somewhere, but I haven’t been able to look at it for a while