Vintage Synth Repair

Hi everyone,

I managed to temporarily fix my power switch problem on the Roland SH-101 until my replacement arrives.  I basically just cleaned it and worked the kinks out by turning it on an off quite a few times.  Now when I rub it, the tuning doesn't falter.  So I think that part is ok for now.

I then found I continued to have tuning issues which was related to a missing screw for one of the PCB boards located over the VR9 tuning knob area.  When I tapped with a plastic screwdriver on VR1 and/or VR2, the tuning would suddenly flip out!  I noticed that when moving the entire corner of the PCB board the tuning would vary.  So I found a screw and tightened up the boards.  Amazingly this seemed to have stopped my SH-101 from getting out of tune.  Wow!  Sensitive is the SH-101!

I then found that when tuning the keyboard I was able to get the lower and upper octaves in perfect tune using VR7 and VR6.  However, I then found that the middle 3-4 keys centering around G were slightly sharp.  I couldn't figure out how to get them in tune until I started fiddling with VR4.  I am not sure if that specifically did the trick, but I do know that after adjusting VR4 and then VR7/VR6 again, the entire keyboard was back in perfect tune!  Awesome.

So, I'm curious. Does anyone know what VR4 does?  Has anyone encountered a similar problem with the central keys not being in tune after making the adjustments as instructed in the manual?  If I encounter the same problem, I'll likely revisit VR4, but I thought I would ask here in case someone might know specifically about the problem or what VR4 does.  Thanks very much!

I can now finally start jamming on the SH-101 in a more consistent fashion.  They sure are fun.  Thanks again.

Jim Atwood