Sustain Pedal Circuit Upgrade -- Pianocorder Forum

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Subject: Sustain Pedal Circuit Upgrade

Author:
Tom Lear

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Date Posted: 18:40:18 02/21/04 Sat

Many thanks to Carl Meyer for sharing his sustain pedal circuit upgrade. I have installed the required components on the playback board.

While I was at it, I removed, disassembled, relubed and adjusted the sustain pedal solenoid.

Previously the solenoid was not performing efficiently and would float on fast pedaling. The upgrade has made a huge difference. The pedaling is fast and crisp as the solenoid is now going thru its full stroke instead of floating.

The concensus among Pianocorder techs seems to be that the airchamber damper system is not needed, and may interfere with the fast response you want of the solenoid. I find this to be true on my installation.

Disassembly and lubing of the solenoid:

Remove the four screws and remove the bottom plate.
Unscrew the adjuster, locknuts, and airchamber cover from the top of the solenoid shaft.

Now you can remove the solenoid slug from the solenoid body.
Clean old grease from the slug, the solenoid sleeve, and the airchamber cup. Relube.

I use a combination of molybdenum bearing grease and 30 wt. motor oil to which STP has been added as a lubricant. This will make it slicker than snot on a doorknob.

There should be only one thickness of the white felt between the slug bottom and the solenoid body.

Place the slug into the sleeve, attach the bottom rest plate.

Lube the air chamber sides. Cut a small piece out of the air chamber cover o-ring, so that the o-ring just fits around the groove in the cover. Lube the o-ring and screw the cover down into the air chamber.

With the solenoid in the engaged position, the top of the cover should be about 1/8" below the rim of the chamber.

With the cut o-ring, friction is eliminated, the airchamber is no longer used as a damper, but I recommend retaining the cover to keep debris out of the solenoid, especially in a upright installation.

Ideally the solenoid should be pushing its slug straight out with no sideways forces on it to eliminate any chance of binding.

Install the solenoid and fine tune the throw using the rest plate and top adjusters.

Tom Lear
San Francisco, Ca.

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