Picked up a Roland ep92 keyboard and needed to clean the whole thing - initially one of the keys was not working.
Dissassembled and had to take the rubber contact strips off the key pcbs as looked like some liquid had made its way in.
Cleaned the boards and carbon contact in the rubbers strips reassebled and all good now except now note G (28th from the left on 88note keyboard) sounds full volume all the time noe of the other keys do this.
I also got an ep7ii which i repairing as now sound through yo amp board. So switched over the 12 way rubber strip from that thinking it might be faulty contacts but repeated the same fault.
Have checked continuity of the tracks nothing broken that i can find.
Measured the keyboard diodes albeit in circuit still and they seem in speck, but thinking to desolder and recheck.
Anyother suggestions??
Going to modify it anyway and install either Zynthian5 or Mini Dexed for additional sounds capability.
Regards
Kevin.
One of the contacts must be faulty and it thinks you’re hitting the key hard.
Check the contacts again and trace the tracks and components.
Otherwise, a new contact board from Syntaur may be the only option.
Thanks will do more indepth investigation on the PCB.
Got a similar problem on an Ensoniq keyboard, where a pair of rubber contacts for each key is used to “measure” the velocity. The culprit was one the contacts in the pair which was dirty.
You should also check the key itself (compare to other ones) to check if when hitting the key both contacts continuity work.
Thanks think its the PCB as switched rubber strip for another one on the same PCB and still got same issue on just that one key.
So going to dissassemble again and reinvestigate the pcb pads again to figure out which is 1st contact and 2nd contact as could see any short last time but for whatever reason on that key its registering maximum velocity. All keys either side work correctly.
Hopefully can sort as dont think car replace PCB as not seen any for that type of keyboard.
Will post more once do further work.
Update,
Took it apart tonight again and carefully used my metre set on diode range and worked through the tracks.
When came to the key in question found that the track to 1st contact was open circuit then upon putting under microscope and very carefully scraping away the carbon where the track entered the pad found that the copper had a very fibe gap in it. Worked before because the carbon very lightly bridged it, but obviously my gentle clean was enough to open circuit it.
Managed to clean enough of copper and use my smd station to put a minute bridge of solder accross then put back together and hey presto problem solved.
Now to tackle the 2 other black keys which are now exhibiting same issue. But know what to look for now.
Thanks for all the suggestions.