GROUND RADIO BULLETIN NO. 32 - JUNE 21, 1951 COMMS. DEPT. L.A.D.
INDEX CARDS - TMC-R/T
We are glad to advise those of you who wish to replace worn and unsightly TMC-R/T index cards in the units at your station, a limited supply of each is on hand in the Ground Radio Shop. They may be obtained by advising this office the number of each required* As they are not in inventory, a requisition is not required.
RFA-50 - 5UUG BIAS RECTIFIER TUBE REPLACEMENT
Data obtained from the Equipment Repair Report forms has shown that the life of the 5U4G bias rectifier tubes when used in the RFA-50 Amplifier, is rather short, requiring frequent replacement.
With a view to finding a satisfactory substitute tube for this equipment, Frank Selin, Station Radio Mechanic, Port of Spain, began comparison tests using a type 5R4GY rectifier tube instead of the 5U4G. These tests, which began the latter part of 1949, have proven this tube far superior to the 5U4G in this application. No wiring changes are required as the pin connections of both tubes are identical.
The PAA Part Humber of the 5R4GY is 9070-3196, and it is presently included in the class 3 Spare Parts Kit. (All stations having RFA-50 Amplifiers fall in this class). Note that the 5R4GY is recommended to replace the 5U4G only in the RFA-50 Amplifier. Other equipment using the 5U4G should continue to do so unless otherwise advised.
MATERIAL SHORTAGES
Material shortages are becoming an immediate problem due to emphasis on the manufacture of National Defense equipment. This applies particularly to all types of vacuum tubes.
So that the situation will not become critical, it is necessary to ask all stations to conserve tube consumption to the utmost. Tubes should be used as long as it is possible to maintain satisfactory communication. This means they should not be discarded just because they appear to be slightly weak. However, it is most important to keep in mind the safety of aircraft first and always.
So, while trying to conserve tubes, try also to avoid communication failures due to faulty tubes. One way to conserve tubes is to reduce antenna coupling, which lowers the plate current, and results in longer tube life# This would be particularly applicable to point-to-point CH transmitters, if the station receiving the signal does not complain of signals being too weak.
Weaker receiving tubes can sometimes be compensated for by increased gain control set-ings. When checking tubes by the substitution method, once the faulty tube is located, make sure that this is the only one replaced, and that other tubes involved are all replaced in their sockets for continued use. Other items such as condensers, resistors, relays, etc., should also be conserved where aircraft safety is not directly involved# Your suggestions and ideas for such conservation will be very welcome.
FORM 9211— 210 7
