JP-8000 A/D test AN5-7 NG error at boot

Synth Repair
1

Hey guys, I think I might need a little help.

I got this JP-8000 that’s got some issues I’m not sure I can repair.

Symptoms are this:
When powering on, it starts with the CPU, DSP, RAM and BATT check, all OK, then it shows a message A/D TEST AN7-9 NG

When I want to go out, it goes bezerk, settings go all over the place and pressing don’t help much until a point the JP demands some kind of action.

If, at this boot error, I go to option 3, the switch/led test, it jumps straight from 43 to 35 with a sound as if all those knobs are pressed at once. From there it’s sometimes possible to finish the 35 button tests while pressing these switches it gives sounds like more than one is pressed, but on other occasions it just jumps test 4 ot elsewhere.

I’ve replaced all the caps, as there was no sound at first too, battery ofcourse, measured the PSU, all the cables, connections, looking for shorts etc etc. I tried to figure out what these AN5-7 means, followed the schematics and replaced all UPC op-amps. This didn’t do much either. I’m thinking to replace all multiplexers as well as the flip-flops, as all these random acting up keys gives me the idea of ghosting (or what’s it called when the matrix acts up and random things happen when pressing keys)

In the mean time I still have no idea what the error message could mean. I haven’t found any kind of information that could help me explain this. The firmware is 1.04, can’t upgrade, as I can’t get into that menu.

I start to fear the mainboard is busted, but I’m nog yet ready to give it up though.

2

I there,

So I went ahead and just replaced all the IC’s on both control boards. That resulted in an new error message: A/D TEST AN7-7 NG, seems like a tiny win, however, that thing with the input gone wild still exists though. And I lost the left channel, but that due to a bad connection from that mainboard connector to connectorpanel. The plastic lid came loose a bit.

3

Another update, I gave up for now. I have the feeling the mainboard has an issue with the HD6413002FP, these are still available, but per 12 where I found them.

I’m not going into that yet and go searching for another working JP-8000 and/or mainboard and go troubleshooting from there. Or not.

So, if anyone has a spare mainboard floating around, either with or without the common errors, I’m willing to purchase depending on the tag.

Any advice is also welcome :wink: