Electric Expression Players(Tuners' Journal - May 1928)
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.
In the servicing of the electric expression or reproducing piano it is most important to keep in mind the control ports on the tracker bar. If these are known and remembered the servicing becomes an easy matter and quicker results will be obtained. These tracker control ports cannot be changed without bringing about a chaotic condition in the music roll, and as the roll manufacturers are committed to a definite policy regarding these ports they must be strictly adhered to.
The control mechanism, such as the re-roll, repeat, electric cut-off, hammer rail and damper lift, is operated pneumatically, and should cause little or no difficulty if the principle is understood. The alignment of the roll may be either mechanical or pneumatic, as touched upon in a previous article in this series.
It is extremely important that a Recordo test roll and a pressure gauge of the mercury or spring type be in the hands of every tuner who would service the expression player (see editor’s Note). There should be no guesswork nor any attempt made to set the different pressures from a music roll. In the mercury type gauge the glass tube and mercury should be kept clean at all times, otherwise the gauge readings will not be correct.
Various manufacturers of expression actions vary somewhat in the setting of the pressures., but on the average there is not a great deal of difference. As a rule, each manufacturer has placed somewhere in the case instructions for adjusting the pressures, which are readily understood, and should be followed carefully. Should there be no instruction bearing on the particular case, and if one is not familiar with the type of action one should not tamper with it but should write to the maker for the necessary information.
Taking the tracker bar from the bass end and numbering from left to right, the control ports are as follows:
Port No. 1 controls the hammer rail lift.
The control ports on the treble end of the tracker bar from left to right are :
Port No. 1 is blank in some actions and controls pressure No. 1 in others.
The pressures in their order run from 7 to 35 inches, and usually as follows:
Pressure No. 1, 7 inches.
Signifying the pressures by pp., p., mf., f. and ff., some run in this order, although there are slight variations: pp., 9 inches; p., 12 inches; mf., 16 inches; f., 21 inches; ff., 25 to 35 inches.
It is suggested that every service man have in his possession a reliable mercury or spring gauge, as well as an instruction manual of the player under adjustment.
On one particular type of expression action the pressures are set in a mechanical manner, or by means of the speed that the roll is traveling over the tracker bar, starting at a tempo of 45 for pp. and ending at a tempo of 100 for ff. For example, pp. tempo, 45; p. tempo, 50; mf. tempo, 65 ; f. tempo, 75; ff. tempo, 100. There is a slight difference in the two types of actions of this manufacture, the large type requiring an increase of one inch for pressure from tempo 50 to 100.
Should it be found that the correct pressures do not build up, it is wise to make sure that there are no pump or stack leaks. Naturally a combination of these two would seriously affect efficient operation of the player. As a test, disconnect the main supply to the pump and stop the supply nipples, and with the power on, the pump should slow down or show slippage on the belt. In extreme cases it may stall the motor. This test should be made very quickly, so as not to injure the pump or the electric motor. Should the pump show leakage, remove and tighten all joints, and, if accessible, all channel boards. Also tighten the pneumatic stack and auxiliary units. In remote cases there may be excessive leakage in the valves, in which event proceed to remedy it the same as in an ordinary player action. To sum up, eliminate all points of leakage and friction, and ninety per cent of the trouble will be removed.
In testing for valve leakage use the same procedure as in the ordinary player action, as discussed in a preceding article in this series.
I use the following method when inspecting a player, no matter what its type or how it is operated:
(1) Test the upper left-hand carrier chuck, and adjust if necessary.
It is assumed, of course, that the piano action is in proper condition. It is impossible to make any adjustments on the player action until trouble is removed from the piano action.
Editor’s Note: It should be noted that the various pressures listed in this article are inches of water vacuum, not inches of mercury.