Knobs, sliders and switches (part 6)
My main goal for this last weekend was to fix everything that was in pieces on my floor. This stuff was not near decorative and I need to clear room for a couch.
So, with parts list in hand, I headed to Norvac (on Nimbus!) Saturday.
The counterperson regarded a knob I brought in and said, "they don't make them in this style anymore." The knob in question was the volume control from an early-80's synth; a 10K dual potentiometer with a serrated end. "Hmm," I said. I told him it was scratchy. "Why don't you get a can of contact cleaner?", he asked.
I did (Deoxit!) and life has been better since.
This pot had been mounted in its parent synth for 23 years and scratched across its entire sweep. A scratch is when the connection between the two wires fed into the pot is broken. This is usually due to regular dust and dirt. Serious damage usually kills the part, so if you can pass any kind of signal through a pot, then it isn't totally broken.
Sliders are equivalent to knob pots except for the "linear" thing. They are easier to clean but are also easier to dirty because they are open at top and gravity is such that junk falls down into their canals.
Switches move between a set number of steps and are also a victim of dirt and grime.
At this point of your synth repair, locate all of the scratchy pots, sliders and switches on your instrument. Label them or just remember. Open your synth; lift the top panel and rest it against a vertical object. Locate the scratchy components in the interior of your synth.
For pots, locate the opening above the wire-post. For switches, locate any open ends or top. If you can reach these areas without unscrewing anything, you win! Usually, though, unscrewing (and even desoldering) is required to expose these parts.
Aim your can of contact cleaner or compressed air at the openings of these parts and apply a short burst into their mechanisms. Turn the knobs and slide the switches for a few seconds and then apply a second burst. Reattach everything you removed to get to the part and wait a few minutes. Replace the lid of your synth.
Turn on your synth and test the parts. If all goes well, they should be unbelievably functional. If they are still scratchy, try the procedure over. If they don't work at all, time for a new part.
Last weekend, I went mad with this stuff. Almost every part I expected to be toasted (or at least browned) sprang back into life. Obscure and unavailable pots, sliders and switches gained a second life.
At the end of the level, though, I had to encounter the mini-boss; the toughest, longest-lasting, least obviously fixable and most annoying bum switch: the volume level selector on my JX-10. This thing has been fuzzing, dropping down, cutting out and generally crap-afying the sound of this pure and subtle instrument since I acquired it two years ago. I looked for replacements, but a miniature three-position horizontally mounted is not a very popular part.
After removing the hilariously mis-matched screws holding the synth together, I located the switch. It is hidden among the many parts boards in a connector daughter-board. Carefully positioning the little straw at the side of the switch, I fired a short burst onto the contacts. Moving the switch back and forth, I shot another burst on the other side. After it dried, I placed the keyboard on its stand (still sans screws) and plugged it in. The sound was clean.