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MMD > Archives > January 1998 > 1998.01.19 > 13Prev  Next


Help for Standard Action Valves
By Bernt Damm

Re: Roger Waring's Valve Problems.  In my opinion, the governor
problem is due to the fact that the internal regulating valve is
not completely tight or cannot seat completely because of some
incorrect adjustment.  Test as follows:

Piano in play, no roll in piano and tracker bar taped close.  Have
someone pump the piano with the roll tempo to full.  Now press the
governor pneumatic closed by hand and observe if the roll motor stops
completely.  It should stop dead before the pneumatic is completely
closed, with a little extra to go.  If it only stops completely when
the pneumatic is pressed closed completely with plenty force, you need
to open it (or set the adjustment screw if present) and correct the
valve to operate properly.

If the motor does not stop at all, there is either a permanent leak in
the valve (warped, scratched etc.) or some seepage between the main
vacuum and the regulated output somewhere.

For the stack problem: You say that the valves suddenly pop onto their
seats and then everything works.  This sounds to me that you do not
have enough pouch to valve clearance.  The valves cannot seat because
they are being held from their seats a little by the pouches in front.

Testing this is difficult because of the horizontal construction of
this action.  Open the front pouch board and measure the protrusion of
the wooden valve lifters forward from the side-surface of the valve
chest (side that mates via gasket to pouch board).  The valves must be
pulled forward for this measurement.  Use a straight edge or wooden
ruler with a piece of masking tape to make marks and then measure.

Next, lay down the pouch board on a table and measure from the side
gasket to the natural dip in the pouches.  Also use a ruler placed from
side to side over the board edges.  Subtract the second measurements
from the first.  If the answer is not at least +1 mm then you have found
the problem.  Screw the valve lifters in till you have about 1 mm
clearance.

Once the optimum is established, all the other valves can simply be
brought in line with the first few samples by means of a ruler and
tape.  This will only work if you have more or less constant pouch dips
throughout

There could be some other causes but try the above first.

Have fun and please let me know if any of this helped.

Bernt W. Damm
Restorer of Automatic Musical Instruments,
Cape Town, South Africa


(Message sent Mon 19 Jan 1998, 20:33:07 GMT, from time zone GMT.)

Key Words in Subject:  Action, Help, Standard, Valves

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