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Testing and Adjusting
The Air-Motor Governor

Problem: The air-motor speeds up when more pedal pressure is applied, causing the music to play faster.

The problem is in the air-motor governor (or just 'governor') or the air-motor control box. There are a few possible problems.

1) The material covering the governor bellow might be getting stiff with age or leaking, preventing it from responding correctly to changing vacuum levels. If so, recover the pneumatic with new cloth.

2) The return spring might be to tense, preventing the governor from closing down fast enough or far enough. (See adjustment procedure below)

3) The knife valve inside the governor might not be seating correctly. (See below)

4) The fast re-roll port might not be closing all the way when the unit is in 'Play'. (See below)

Adjusting Procedure

To test, have someone else pump the unit evenly and depress (or collapse, or close) the governor by hand. When depressed all the way, the motor should almost stop (with tempo set to 60-70).

To insure that the stop screw, which prevents the governor from closing too far, is correctly adjusted, turn it 'out' one-half a turn at a time and test it again until the motor does stop when the bellow is fully closed. If the motor does stop when the bellow is collapsed fully, turn the adjustment back 'in' one-half turn. When adjusted correctly, the motor should just barely crawl when the vacuum level is high.

If the motor never comes to a complete stop, the problem is in the adjustment of the fast re-roll valve (or the valve itself) or with the knife valve inside the governor. To eliminate the possibility of the fast re-roll valve as being the problem, open the control box and visually check the position on the fast re-roll valve while the unit is in the 'play' position. It must cover the air-port 100%. Also check the integrity of the leather. It must be smooth and slightly flexible to make a good seal. Reassemble everything and test again. If the motor still fails to stop, the knife valve is the problem. Open the governor and inspect the surfaces of the knife valve. They must be smooth and make positive contact with each other. Clean and re-graphite as necessary. Reassemble and test. If the motor STILL refuses to stop, there is a leak somewhere in the control box which is allowing vacuum to bypass all the above controls. Seek out and eliminate the leak.

To adjust the governor once all of the problems have been eliminated, you need a Test Roll to calibrate the governor and the control box. As a preliminary adjustment. Set the tempo to "0". The motor should stop. Set it to "10", the roll should 'creep'. Set it to "70" and measure the time it takes for the roll to travel 7 feet. It should take one minute.

Now set the tempo back to "10" and pump hard. If the motor stops, turn the air-motor governor stop screw in a bit until the motor 'creeps' along.

Once the stop screw has been set and the "0" and "10" settings are working correctly at all levels of pressure, then the governor spring can be adjusted. Set the tempo to "70" and test as described above. If the unit speeds up under heavy pumping, decrease the spring tension. Then go back and retest all the above settings to insure they have not changed. If so, re-adjust and then start the "70" test again.

Keep going back and forth until all three settings stay constant at all levels of pumping pressure. These adjustments are all interactive so any change in one will effect all three settings. It's a delicate balancing game and all components of the system must be in excellent condition before the final result will prove satisfactory.

- - - - - - - - - Added Notes - - - - - - - - - -

Sometimes it can be a pain to get the Tempo Indicator correctly adjusted to the position of the sliding tempo valve. Usually, there are four adjustments. 1. Where the pointer mounts on the tempo rod. 2. Where the tempo rods is secured to the upper lever arm. 3. Where the horizontal tempo rod connects to the lower lever arm. (Sometimes this is solid metal, or a bent rod. So it cannot be adjusted.) 4. An inline adjustable link between the lower lever arm and the Tempo Actuating Lever -Or Tempo Control Rod.

Also, the rod going into the Tempo Control Box is almost always threaded, which allows you to make fine adjustments without changing any of the main linkage.

The main thing to remember is the all of the levers and arms should be positioned such that at their middle position of rotation (or the middle of their arc), the Tempo should be at 70. If such is not the case, the Tempo will be less linear than designed by the manufacturer.

FYI, when you start changing the adjustments, start from the sliding valve and work towards the Tempo Indicator, not the other way around. Make sure the Tempo Lever (in front of the keys) is position straight up, and that the other lever at the rear of the rod is pointing straight down. (Sometimes the position of the rear lever is adjustable.)

Also, understand that the function of the air motor governor (AMG) also comes into play during the entire adjustment process. So, getting the governor to work correctly at 70 is a prerequisite to adjusting the "0", "10", and "70" tempos. This is because the functions of the AMG and the Tempo Control are interactive. So, using a test roll (or a roll that has a mark at every foot) should be played at different pedal pressures to insure that it stays at '70' whether you pedal softly or loudly. The importance of this cannot be over emphasized.

BTW, normally there is no bend in the rod that connects to the tempo slide valve. Or, if there is one, it is very near to the sliding valve, i.e. within the last inch of the rod just above the sliding valve.

Other Tests/Checks
Testing the Stack
Testing the Air-Motor
Testing the Lower Section
Testing the Tracking Device(Not Done)

Now Playing: This MIDI file is called " Saved by Gabriel " and it was created on May 17, 1998 after hearing the song on an old cassette tape. Gabriel Della Fave converted the audio cassette to Real Audio and I wrote the midi file the next day. Like many of my tunes, this one never had a title until now.

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This page was last revised March 6, 2013 by John A. Tuttle, who Assumes No Liability
For The Accuracy or Validity of the Statements and/or Opinions
Expressed within the Pages of the Player-Care Domain.
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