Richardson's handbook of projection (1930)

MANAGERS AND PROJECTION J S TS 1369 show that trouble exists here, and this must be corrected before anything is done to the 41. Should the condenser Cll become shorted, it will be indicated on the 41 amplifier by no plate current in any of its tubes. An open in the choke LI, or in the wiring from the choke to the three buttons used to put the meter in the circuit, results in no current at the tubes. In event the choke LI becomes shorted, no trouble will result unless it happens that the 42A is overloading, in which case it might cause distortion because of the drop in potential of current going to 239 tubes. Choke LI and condenser Cll normally tend to keep the plate current voltage to the 41 steady. Bad contacts in the switches (operated by buttons) cutting the meter into the plate circuits will cause noisy reproduction. It may cause loss of sound entirely. Any one button will only affect the circuit connected to it, of course. The current shown by the meter is not always the current value flowing through the tube. For example : if bypass condenser CIO becomes punctured, the needle will go off the scale, because of the comparatively heavy current flow to ground. The tube, however, would be getting no current at all. When the tubes are all right, the filament circuit likewise and the current adjusted to 270 units, the cause of a high reading in any of the stages are (a) Supply voltage above 390. (b) A ground, (c) A shorted resistance, (d) A shorted bypass condenser of any of the plate circuits, (e) A shorted stopping condenser. -That is to say the condenser between the plate of VI and the auxiliary