Vintage Synth Explorer Forums

Hello,

My Roland SH2 just went crazy without a warning.

Symptoms are:

-It does make a sound, however the sound has no pitch control, so no matter which key I hit, it has the same pitch.

-Range knobs have no effect except osc 1 goes really dirty on 16´

-Waveform knobs have no effect either except noise on osc2 sounds like a dirty saw

-Sub osc makes just the same weird sound as all the others.

-Envelope, filter and LFO modulation work partially, so I can make the filter self oscillate on that weird sound, but it does not mute it if I close the filter. Envelope does control the sound and filter only to a point, but it feels as if there were 2 sounds stacked.

-Most interesting problem is leaking sound when I hit the keys. By leaking sound I mean a sound that comes out even though all the oscillators are turned down. (its on filter self oscillation either). It sounds pretty much the same when you touch a cable end that is connected to an amp and it makes this dirty saw leady sound.

-Basically all the controls that should change the pitch, only makes the sound go dirty and weird.

-It has been in my studio, in a dry and warm environment for the past few months, so there should not be any recent stress from touring.

If anyone has any idea how to troubleshoot this, it would be highly appreciated. I try to start solving the problem and I keep you updated if I find any solutions.


-Johan

Hi

It sounds like it's really decided to throw a tantrum. Considering that it's refusing to track the keyboard, and that both oscillators have gone at the same time I would considering checking the Keyboard Control Voltage circuit. It's on the OPH64 board, page seven of the manual which can be found here:

http://manuals.fdiskc.com/flat/Roland%2 ... Manual.pdf

Look for the KCV test point there and follow the calibration method described a bit further down on the manual. It's just the usual 1volt/octave design. See if the voltage is in a normal range and that it changes accordingly. If it doesn't, there problem ought to be easier to pinpoint.

Hi

Thank you for the information! I really think you right about the problem with tracking since, although I haven´t had time to do the checks on the circuits, I tried it with external cv/gate control and it works just fine.

I´ll post more info, after I have checked the circuits.

-J

Oh good that narrows it down even more. There are two op-amp/comparators (can't tell what the actual chip is) and FET in the CV circuit that I would be my primary suspects. See if one of the ICs is unusually hot (if you can get to it safely - may just be better to replace both if they're common)