Keyboard repair

Here's a couple things you can do to beat that old electric piano back into shape:

1. Clean the contacts on the keys. Under the key, at least on a velocity sensitive keyboard like this Ensoniq SDP-1, there is a spring that makes contact with a busbar. The bar and the spring will corrode and get dirty. Use contact cleaner and an old toothbrush to scrub them gently until they shine.

2. Check electrolytic caps ESR and replace as necessary.

3. Check the “action” springs (the ones that return the key to its original position) for weakness and replace as necessary.

4. Check the amplifier jacks and make sure the retainer mechanism is in place, usually a thin nut that threads around the outside of the jack. If this is missing, the jacks will eventually break off the PC board. (The replacement part number for surface-mounted 1/4″ mono jacks is Kobiconn 16PJ500.) It also would not hurt to reflow the solder between the jacks at the board as a preventative measure.

I make my own patch cords out of bulk 20 gauge coax instrument cord and bulk spring-relief ends.

To do this, take a length of cable, cut the outer jacket away about 1″ down, twist up the outer strands, and then use a wire stripper to remove about 1/2″ of the inner jacket. Take an end and insert the cable into it, getting some of the strands for the outer/ground part through the ground hole and some of the strands for the inner/signal part through the signal hole, and bend the strands around so they stay (and aren't touching the wrong part of the jack). Use a pair of pliers and “crimp” the retaining clip around the cable. Now apply a bit of solder to both holes, securing the strands into the hole. Slide the plastic insulator sleeve over the junction area, then screw on the outer shell and the spring strain relief.

Do the other end in the same way and give the cord a test by wiggling both ends while playing, there should be no drop-outs or fuzz in the signal. Congratulations, you just saved $20 or more…

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