GROUND RADIO BULLETIN NO. 34 - SEPTEMBER 12, 1951 COMMS. DEPT. L.A.D.
4-250A TUBES -
Somewhat over half of the Division stations using 12GLX2/12ACX2/GM8 equipment, have now been converted to operate with the 4-250A tube in the power amplifier stage.
So far, improved all around operation has been the result of the modification. In this connection, reports are requested concerning individual station experience with the new tube. Of particular interest is the balance being maintained between the two tubes in a transmitter. Please report any unbalance that has developed. This particular trouble was quite common with the RK65 tube. Also, any other irregularities in the tube performance and operation are subject to reporting.
It is requested that hours of operation be recorded for the time being wherever the 4-250A tube is used. The hour counter is suitable for this where non-standby filament operation is in effect. Otherwise, such time can be computed by the operating schedule of the equipment. Where dual equipment is concerned allowance should be made for alternate operation which will usually halve the total hours of each transmitter.
While no tube failures have been reported as yet, when this does occur, the service sheet that is supplied with each tube should be filled out and forwarded to the Division Communications Superintendent.
All reports concerning the tube can be made on the regular Equipment Repair Report sheets provided for each transmitter. Be sure to mention the tube manufacturer, whether Amperex, G.E., or Eimac.
AAM
Lucien Prudent, Station Radio Mechanic, Cayenne, has called attention to an error in the AAM Receiver Periodic Overhaul sheet (CD319D), in the Maintenance Manual. Please refer to the Receiver Section (9), page 240-2. In the cathode voltage section, column EK opposite item 73, (6SJ7 DET.) it will be noted that the cathode voltage is stated as being 200 volts with Max. Vol. with signal, and 15 volts with Max. Vol. without signal. Pending correction of this sheet in the manual, please change these readings with pencil to read: 20 volts with signal, and 15 volts without signal.
These are average readings.
FORM 9211— 21 07
