Midphase
Member
Working on a Korg Poly 61 (non MIDI version) which has one of the strangest issues I've come across -- up and down the 61 keys, everything appears to be transposed up a perfect 4th. There are no tuning discrepancies across the octaves, but obviously since hitting a C yields an F, this is not a desirable thing.
Rest of the synth appears spot on, working 100%. Voltage out of the power supply also appears to be exactly where it should be, looks good under load on both my multimeter and my scope.
Before some of you chime in with the dreaded exploding battery issue, this has been addressed by a previous tech and there doesn't appear to be any damage worth noting.
I already fiddled with the various tuning knob and trim, and looking at the pitch bend assembly everything looks fine there. The client is telling me that the synth was working perfectly until this issue started about a week ago out of the blue.
Since this is affecting all of the voices across the board, and all of the presets, I suspect some type of IC or other voltage controlling component that affects the entire tuning voltage of the synth globally.
The service manual that Korg made is a mess honestly, and there aren't a whole lot of instructions for dealing with something like this.
Any thoughts? Has anyone run into a similar issue whether on this or other synths that might give me some inkling as to where I should be looking next?
Many thanks in advance!
Rest of the synth appears spot on, working 100%. Voltage out of the power supply also appears to be exactly where it should be, looks good under load on both my multimeter and my scope.
Before some of you chime in with the dreaded exploding battery issue, this has been addressed by a previous tech and there doesn't appear to be any damage worth noting.
I already fiddled with the various tuning knob and trim, and looking at the pitch bend assembly everything looks fine there. The client is telling me that the synth was working perfectly until this issue started about a week ago out of the blue.
Since this is affecting all of the voices across the board, and all of the presets, I suspect some type of IC or other voltage controlling component that affects the entire tuning voltage of the synth globally.
The service manual that Korg made is a mess honestly, and there aren't a whole lot of instructions for dealing with something like this.
Any thoughts? Has anyone run into a similar issue whether on this or other synths that might give me some inkling as to where I should be looking next?
Many thanks in advance!
