Sometime ago i bought Roland’s first ever synthesizer, for about a quarter of what it goes for these days-it was in dire condition, mind you. The control panel rusty and battered, the silkscreen on a couple of spots barely readable.
I always believed mint condition items belong to museums, not being fit for use, abuse and misuse.. i feel the same way about vinyl records-people who wrap them in polypropylene covers from day one and treat them as if they’re going to break anyday soon.. good grief
I must say that although i truly love the instrument- i also fit the Kenton cv/gate control board a year ago, i rarely ever used it.
The other day i took it out for a spin and the tuning was way off, it was drifting. It wouldnt even span an octave-it was that bad.
Time to recap, i thought, and pulled out the Elnas, the Nichicons and the soldering iron-i figured i’d refresh the power filtering section, part of what the service notes call the “Pulse Sheet Assembly”..
Just a note for the caps lovers: although the unit was in working condition, even if out of tune, most of the 1uF caps on this board were way off their nominal capacitance-the 2.2 uF cap measuring a whooping 8.5 uF! Of the big 1000 uF caps, two were measuring 1200something uF, whereas the other two were still closer to the 1000 mark-and they all showed low ESR (40+ year old caps!). The three tantalum capacitors on this board were still working great, their value as per specs.
I fired the synth after recapping this board-the sound was a bit more definite, but the tuning was still off.
I decided to check the VCO board, pictured above. But, alas, no electrolytics there to substitute. I checked very carefully the board-and there it was, staring at me: A BROKEN DIODE.
The diode+resistor combination to the upper far right of the board: the diode was broken in two!
The schematic calls for diode, 1S2473.. i checked a few diodes I had, and landed on a 1N4148 as a fitting substitute!
And.. yes now it IS tuned! The snipped diode was the issue!
Assorted pics of the wiring at the back of the oscillator board
Masuto's 
Hi! Great info!
I’m trying fix my sh1000 to and it is out of tune.. But a little different… even after waiting some minutes to warm up (and all modulations off), its osc isn’t stable… It sounds like the portamento were on and slow. I need to solve that first before calibrate it… Could you help me, please?
Hello and sorry for the belated reply.. have you tried recapping the electrolytics in the psu and vco section?
Recap and make sure your voltages correspond to the service manual expected values