Roland Promars - strange slow pitch drift

[zingo]

Hello everyone, I wonder if somebody has any ideas about the following problem. A few days ago, I noticed that the main oscillator on my Roland Promars was slowly dropping. By now it's approximately three octaves below normal pitch and the instrument is unusable. The Roland Promars is basically a monophonic, two-oscillator version of the Jupiter 4. Everything else seems to work fine, including the tuning on the second (auxiliary) oscillator. Looking at the service manual, my best guess is that some component on the module board for the main oscillator (OP-106) is slowly failing but any ideas which components to primarily suspect would be greatly appreciated. I know this synth is quite rare, but as far as I understand it this board is very similar to the four found in the Jupiter 4 (I have one, and it certainly looks very similar). Perhaps someone has experienced a similar problem with their JP-4.
Kind regards.

[shaft9000]

not a promars/JP-4 guy myself,
but this seems like a capacitor problem. i'd replace caps in the PSU too; heck, all of them. a capacitor is basically like a battery although it lasts longer - so caps will wear out (depends on type, but commonly after 15-20 years) no matter what. result is the synth often gets noisier, more and more out of tune etc

[zingo]

Thanks - I'll begin with looking at the capacitors then.