Fixin a Korg SQ-10r
The Korg SQ-10 is an analog sequencer from the late seventies. I have it for a while now, but I always was disappointed by something anoying: when I was driving a VCO, I had a significant pitch drop between step mode and continuous mode. I measured 1 volt of difference between the 2 modes.
I opened the unit to check the PSU and quickly noticed the presence of a 7814 on the negative rail, in place of the expected 7915 (minus 15 volts voltage regulator)! Minor incidence during some operations, but it was clearly perceptible in continuous mode.
(-14 V)----(0V)----(+15 V)
As the solder joints were "vintage", I think the mistake has been done at the factory back in 1979!
Anyway, an easy fix. The SQ-10 is now providing the correct voltages.