Ensoniq TS 12 Keys not playing

Good evening,

My not often used TS12 is showing the follwing symptoms.

once turned on, all keys play fine, but E5 through to B5 (8 notes in all) are problematic.
Once in a while theyll play on startup but only after Ive played the notes a few times till they come good. then after some time they go dead and remain dead.

Any suggestions as to how to tackle the issue is much appreciated. reagrds Emmanuel

keyboards of polyphonic synths are scanned by the CPU as a 8x8(x2) matrix. So if you are missing eight keys in series, it is quite likely that the corresponding wire or pcb trace, which connects the common line of those eight keys to the CPU is broken.
I don’t have a service manual, so I can’t give you more details.

Thank you vry much for your reply.
An interesting quirk that ive noticed though is that when i initialy power on the synth it will play those notes for a moment and then cease to play them again.

Im not sure im diagnosing correctly, but should i be looking at the switches under the keys, or the ribbon cables etc

cheers Emmanuel

The synth is of the age of multiple age related component failures.
First, find a schematic.
Check all wiring for bad or cracked solder joints.
check the main power supply capacitors and then the electrolytic capacitors on the motherboard for obvious leaking,
Then check the tantalum capacitors for shorting, fire or other issues. Tantalums failure without any visible indications so they all need to be tested. They are a royal troublesome pain in the a$$ but every one needs to be checked.

Sounds like a bad capacitor.

Thank you for your reply as with all the others.
I will find some time over the next few weeks to pull it apart and do a cap replacement . Ill try and source a schematic of the ts12 to better trace the possible fault .

cheers Emmanuel