Hey Guys I have an SQ-80 that started exhibiting some strange behavior. Hoping you can help.
I turned it on one day and noticed that I got a ‘low batttery’ warning and the data slider wasn’t working. I replaced the slider and at first, nothing worked. I noticed then that the pitch wheel was only bending down, and the mod wheel wasn’t working at all. Then after a soft-reset the slider started working, but not going through the full range of values. After two more soft resets the data slider, pitch, and mod wheels were all seemed to be working OK.
The battery tested at 2.8v, but I was still getting that low battery warning so I installed a new battery.
Now, back to the same problem - and this time I can’t get anything working again. Data slider doesn’t work, pitch and mod wheels do not work at all. Every time I turn the synth on i get the ‘low battery’ message, even with the new battery (that tested fine at 3.1v) I’ve tried resetting the machine several times with Record + Top Left Button. I even tried the hard reset, jumping R1 to the lower left pin on UC50. No luck.
No values change in the analog test screen (Record + Compare) when I move the pitch and mod wheels. All values, including ‘BAT’ are 255.
All filter values are ‘000’ in the filter tuning screen (Record + Filter)
I tried reseating all the connectors. Even cleaned all the contacts with de-oxit. Still no luck.
Also tried popping in my old Eproms (I’d upgraded to 1.8) - same issues.
Stranger yet - everything else on the machine works. I can load patches from disk, all the keys and buttons work, aftertouch is working, screen is a-ok, and I’m getting sound out of the outputs.
Looking through the service manual, the issues seem to point to a problem with the power supply or main board. There’s a guide for trouble shooting the PSU, but I wouldn’t know where to start diagnosing the main board.
No idea where to go from here. Any assistance would be greatly appreciated!