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Electric Reproducing Pianos (The Duo-Art)
(Tuners' Journal - Cont. from March, 1929)

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.

The Duo-Art

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
With the sustaining and soft pedals in their "On" position the wedge dampers should clear the strings at least one-eighth of an inch and the hammer rail should move forward to within one inch of the strings. In the grand, the hammers should lift fiveeighths of an inch from their normal position. Spring No. 1, illustration "N," page 37, controls the speed of the sustaining and soft pedals in the upright, and spring No. 20, illustration "P," page 41, controls the speed of the sustaining pedal in the grand. (See comments on Modulator Control Pneumatic in THE JOURNAL for March, page 402.)

Accordion Dynamics
With the Duo-Art switch lever at the "On" position, the accordion dynamics should collapse in their order, Nos. 1, 2, 4 and 8, on both the accompaniment and the theme sides. Should they fail to operate in their given order test directly at the primary accordion valve box, removing the tubing leading to the dynamic that is not operating, and correct.

Accompaniment Zero Setting, Tempo 80
As this setting is the most important, it is essential that on the first arpeggio test the notes should speak evenly, distinctly and softly. Watch for weak notes in the second run, and correct if too loud. When making adjustments, do not tamper with the leather nuts on the accordion dynamic support rod. ( No. 14, illustration "E," page 17.) They are set correctly at the factory, and should be left alone. Regulator springs Nos. 2 and 35, as well as all other springs, were covered in a previous article in this series. Carefully read instructions on this test, pages 23 and 24 of the service manual.

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
As previously stated, the theme zero setting is one degree louder than the accompaniment. When adjusting the theme zero setting follow the same procedure as when setting the accompaniment. It will be noticed that the loud pedal is on with the first run of notes on the theme arpeggio, then off with the next run, making it considerably harder to play than the accompaniment run with the loud pedal off. The reason is because the notes are shorter and consequently play faster. In the second run of the accompaniment with the loud pedal off there are nineteen notes played and in the theme run, with the pedal off, there are fifteen shorter notes played in one-half the space. It is easily seen that more pressure is needed to play the second run of the theme with the pedal off and the shorter notes. If the theme zero is then set so that it plays about every other note on the second run, with the pedal off, the one degree louder has been obtained as described in test No. 8, Theme Zero Setting, page 24, of the service manual. If both accompaniment and zero settings are properly regulated the accordion dynamic chord test which follows will meet the requirements of the chord test in the roll. Note tests carefully, and also test reroll and repeat in the order given in the service manual.

Key Slip Control Levers
Test key slip manual control levers to see that they move freely and do not bind. In extremely damp weather the bushings may become swollen, when the levers will bind. This binding must be eliminated, as any constraint in the freedom of these levers will affect the movement of the knife valves in both the accompaniment and theme regulators.

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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This page was last revised March 9, 2021 by John A. Tuttle, who Assumes No Liability
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