Regulating Ampico A
By Bruce Clark
Don Teach asked how would the Ampico restorers suggest regulating a model A Ampico from scratch. Hi, Don, I see that no one responded to your request, therefore, I will write down my method.
First, I will say that the Ampico test roll gallops along so fast, that it is difficult to keep up with. By the time a test passes on the roll, and you try to take a reading, the roll is performing the next test. If you slow the roll down, or stop it, the air motor does not use air, and the readings are not correct.
Here is how I go about the job. Assuming that the crescendos work properly, and there are no leaks in the unit valves or other places, and all is working properly: You must have a very good and accurate vacuum gauge. Without it you can not make an accurate adjustment.
1. Cover the entire tracker bar with drafting tape, or a tape that does not stick severely.
2. Trick the take up spool so that it thinks there is a roll on it by applying more tape, either to cover the port on the take-up spool, or to trip the pallet valve (on uprights). Turn on the motor and set the control to the play position.
3. Set the Modify switch at medium, Ampico switch at on, Pedal on.
4. Set the tempo at 65. (I say this because the air motor uses a lot of air and will have effect on the reading. There are other reasons, but I will not get into a lot of complex theories and confuse you at this point.)
5. Using a tooth pick, carefully prick a hole in the tape that covers bass end holes 2B 4B & 6B in the tracker bar, and do the same in the treble end. 2B is the second hole in from the left, 4B is the fourth etc. The same in the treble section, counting from the right. Prick a hole at 2T 4T & 6T.
6. Remove a hose on a unit valve, on the bass end of the stack and check the reading on the gauge. With the intensities tripped, and the modify switch set at Medium the gauge should read about 19 to 20 inches of water vacuum. To adjust this, slightly rotate the spill valve spring (the spring closest to the amplifier pneumatic) in very small turns right or left, to increase or decrease the reading. Check the treble end, and the reading should be the same.
7. Set the modify switch to Brilliant. The reading should increase to between 27" and 30". To adjust this, use the large screw in the top of the amplifier pneumatic, turning it in to lower the reading, and turning it out to raise the reading. (The small valve box that controls the amplifier pneumatic can be a source of problems. Make sure that it turns on and off properly)
8. When this is done, check it again, to be certain all is working well.
9. Cover the ports where you pricked holes with more tape, and shut off the motor. This should cancel any intensities. Turn the motor back on, and prick a hole at 3T which turns on the soft pedal. Taking readings at a unit valve in treble or bass. The reading should be about 7" of water vacuum or lower if possible. Low enough that the softest notes play very softly but do not drop out. Adjust this lower level by adjusting the springs on the Crescendo pneumatics.
10. If you have a test roll, you may now use it to test repetition, crescendos, soft, and loud pedals. Any notes that do not play or repeat softly on this test, may or may not have unit valve problems. Usually the problem can be traced to a dirty bleed, or leaky unit valve. Other times the problem can be in the piano action itself.
11. Tempo test. "Tempo 60" is six feet per minute, "Tempo 70" is seven feet per minute. If you do not have a test roll, mark an old roll in feet, and time it with the second hand of a clock or watch. Adjust accordingly, so that the marking on the tempo pointer is correct.
I hope that this will be helpful. If you have any problems, please feel free to contact me.
Bruce Clark
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(Message sent Fri 28 Feb 1997, 13:33:54 GMT, from time zone GMT-0500.) |
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