Roland SH101 CPU problem

earo · Joined: Apr 19, 2011 Posts: 13 Location: haifa

Hello y'all Smile

I'm trying to fix my old trusty SH101. The power switch was faulty and I replaced with a 6 pin switch (from Vintage Synth Parts). That went quite well and now the drifting pitch problem is resolved and the VCO is stable again.
However, it seems the Arp/Seq section is dead. All the LEDs are off and none of the functions work. My first suspicion was that the CPU IC was busted, but being that the key assignment works, the keys are scanned and the VCO responds typically (which is one of the CPU's duties) I guess it does work, at least partially.
I looked for more tips in the service manual but still have a hard time figuring this one out.
Anyone here has any experience with these and could suggest a procedure (or solution) for this? Thanks!