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#937 Inline Amplifier
(6/1/24: Will make this part on demand)

THE AMPLIFIER. Inline booster for 5/32" tracker bar tubing. Here's a handy item that is a must for every toolbox, when you go out of the shop for on-the-spot repair or trouble shooting, and you don't have the time or want to tear the action or device down until a later date. Say, the loud pedal is sluggish or a note in the middle of the test roll doesn't respond well. Maybe a snare drum beater with no zip. Maybe you don't have the tools and supplies to properly attend to the problem at the moment. Whatever the reason, the #937 Amplifier could be the answer to the immediate problem.

It's worth a $32.00 investment to be prepared. These problems will eventually happen and you will be glad you're ready.

Then, the next time you do have the occasion to work on the instrument, you can repair the porous pouch, shim the lifter disc, right a crooked valve, or locate and repair the pinched, clogged, or kinked signal tube leading to the valve. Then you can salvage back this unit for the next on the spot fix.

For the here and now situation, the 937 will get you by as long as disconnecting the signal tube, leading to the valve, gives you the desired response, with the signal tube being fully open. That's because this booster will do the same thing when put inline, close to the troubled device.

It works very much like a primary valve, but does not require a separate vacuum supply; it works on the vacuum already in the line caused by the bleed that's connected to the pouch it's supposed to operate.

Vacuum above and below a pouch in the 937 is equalized by a bleed inside the 937. The weak tracker bar signal, as long as it is slightly stronger than this bleed, will allow the pouch, in the 937, to suck up towards the upper cavity where the greater vacuum is; because the tracker bar opening overcomes the vacuum on the lower side. In the process of the pouch inflating, it lifts a flap valve to the atmosphere which is fed directly into the opposing tube. When the tracker bar is again closed, the balance is quickly restored and the atmosphere flap goes back to closed position.

This is a very compact unit. Size: 1-3/8" x 1-3/8" x 5/8". Works in any position, any place in the line; just sever the offending signal line somewhere near the sluggish valve, and insert the No. 937. Works like a charm. Works like a primary valve.

No. 937: $32.00

How it works

Basically speaking, the amplifier is a primary-type valve that turns a small, weak signal into a larger, more powerful signal. The 'valve' in the unit is comprised of just a pouch and a small flap of thin pouch leather. When the pouch inflates, it opens a hole in the top of the unit which is much larger than the hole in the trackerbar. That larger atmosphere signal thens triggers the valve in the device that needs the stronger signal to operate.

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This page was last revised August 8, 2019 by John A. Tuttle, who Assumes No Liability
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