Hi there - I have a JX-3P that I purchased used about a year ago and am finally getting around to attempt to figure out the issue. It looks like just about everything works on the synth, except patches 1-8. I know the LEDs are working, as hitting write lights them up. I’m not very knowledgeable on the insides of a synth but can solder and do the 101s of synth repair. Thanks for any and all input on how to fix this.
Did you ever figure out your issue? I have the same problem, but 1-8 will come on after awhile and are able to be selected, but eventually go out again. I’ve seen nothing obvious on the inside, and 9-16 work and the unit itself has no other problems.
The buttons for patches 1-8 share a common connection to CN6. It’s a 9 pin connector, but they’ve labelled pin as 51.
It could be a bad solder joint on one of the connectors to that cable, a broken wire, or a problem with IC34. You might not see it in a visual inspection. I’d start with reflowing the solder on that line and see if that fixes it.
It could also be some flaky pushbuttons, but I’d expect to see more of them bad - not just one column of the matrix.