Tuesday, March 25, 2014

SH1000 Sample and Hold repair


A friend asked me to look over a ROLAND SH-1000 prior to a tour. I happily found and replaced the sample and hold capacitor (the only polystyrene one - on tall legs with rubber sleeves). The hold had started to drift downwards faster than one would hope. Given that it is simply a capacitor (albeit a low leakage one) storing a voltage that keeps a note sustained when the HOLD switch is on, downward drift is inevitable as the cap 'leaks'. If this is too much for you - i.e. you need a LONG drone - a matchbook (or finger) holding down the same note will produce a steady control voltage and your note won't change pitch. This downward drift is a limitation (or feature) of some early synths and is caused by the physics of capacitors themselves and is not a tuning issue.