Electric Reproducing Pianos (The Duo-Art)
By Wilberton Gould, Member N. A. of P. T., New York City
Service, as defined by Webster: "An act of one who serves."
It is one of God's greatest gifts to mankind, for who is happy who does not serve? Hence it follows that service requires sacrifice. It is the foundation stone of every enterprise. Whatever it may be, its success or failure depends upon whole-hearted co-operation.
And may service and sacrifice continue to be the keynote of our progressive Association.—The Author.
While it is not intended in this series to deal with grand and upright action regulating, attention should be called to the fact that the more knowledge the technician has of action regulating the better equipped he is to service the piano. A well-regulated action is a pleasure and a joy not only to the manual performer but it is an absolute necessity in order that the best results may be obtained from the reproducing mechanism. Conversely, a poorly regulated piano action is an abomination both to the performer and the hearer, and will defeat the best efforts of the technician to adjust the Duo-Art mechanism.
Therefore, before attempting to adjust the Duo-Art it is absolutely essential that the piano action be in proper regulation. See that the hammers travel correctly, that all flanges are tight, and that the junction block under the key bed on the grand is tight in order to avoid leakage. Inspect all supply tubings for leakage. Be careful not to overhaul any of the screws. Clean the spool box gearing of dirt, grease and oil, and inspect the ladder chains for excessive lag. Do not squirt oil on the transmission. This is bad practice, as if oil is used it is apt to reach the gum tubing, in which event it is bound to destroy the body of the tubing. Use a good quality of lubricant, but not too much of it. Do not use oil or grease on the air motor.
On new set-ups or demonstrations be sure that the correct type of electric motor is installed in the instrument and that the voltage and cycle are correct. Eliminate all undue motor noises, see that the belt travels true from the motor to the pump and that it is just tight enough that it does not slip on a full load. In the later types of the Duo-Art the belt slack is taken care of automatically by springs, while in the older types provision is made for taking care of this adjustment. Make sure that the motor frame does not touch the piano frame, as this would cause an annoying motor hum.
Be sure to pump out the tracker bar ports with a reliable pump.
Place a Duo-Art test roll on the carrier shaft and with the lever at "Play" and the tempo at 0, test for quietness. Eliminate any undue noise. Set the tempo at 70, and with the roll running test the speed of the tempo ; correct if necessary. On this test the Duo-Art lever must be at the "Off" position, and the test roll should run seven feet a minute, or three and one-half feet in one-half minute. If the tempo is too fast decrease the tension of the governor spring, and if too slow increase the tension of the spring. (Refer to illustration "M," page 35 of the 1927 service manual.) The tracking device may also be tested at this time. (Refer to pages 32 and 33 of the service manual.)
Sustaining and Soft Pedal Test
Accompaniment Zero Setting, Tempo 80
Adjusting screws Nos. 7 and 8 are of different colors, one being blue metal and the other white. (See illustration "F," page 18.) Screw No. 8 is a lock screw and must be loosened before it is possible to adjust the movement of the knife valve, through the medium of screw No. 7. Failure to loosen screw No. 8 is apt to damage adjusting screw No. 7. After the arpeggio test is set correctly tighten lock screw No. 8. In the upright model turn screw No. 7 to the left to make the tone soft, and to the right to make it loud. On the grand, turn adjusting screw No. 7 to the left to increase and to the right to decrease the volume.
In setting the arpeggio test as above, observe the movement of the accompaniment and theme regulator pneumatics. As the volume increases the pneumatics will tend to close, and as it decreases they will open. This applies to both grand and upright models.
Theme Zero Setting
Key Slip Control Levers
Now, a final word about any and all adjustments and regulations of the reproducing mechanism : know what you are doing and why you are doing it. Be honest with yourself ; if you do not know how to make the adjustments do not attempt them. It will be safer.
Any questions on the operation and adjustment of any type of the Duo-Art mechanism which a service man desires to ask will gladly be answered in THE TUNERS' JOURNAL through the department devoted to such inquiries.
This completes the articles on the Duo-Art reproducing piano.
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