GROUND RADIO_______________BULLETIN NO. 8 - july 27. 1949 COMMS. DEPT. L.A.D.
5IN-2 HUM AFTER MAKING MODIFICATION "A"
Recently, after making modification ,rAn to the Collins 5IR-2 receiver, several cases of excessive hum have been reported* A recheck of Dwg* GEN-9A-1016 gave no clue as to the cause, since the instructions were correct« A memo was sent from this office requesting any corrections that might have been found in the field.
Max Fiallo, Station Radio Mechanic of Ciudad Trujillo, answered with the solution«
The condenser C134 is supplied by Collins, and was supposed to be the exact replacement. The condenser supplied has the common (ground) terminal at one end rather than in the center as shown in GEN-9A-1016.
Therefore, if you have made the modification “A” and have experienced excess hum, check this condenser C134- Make sure you have the common terminal grounded. If you are expecting to make this modification in the near future, make a notation on GEN-9A-1016 to check the C134 before installation.
AEROPHARE
The station aerophare installation is of such importance to aircraft that all personnel should assure themselves that their equipment is in faultless condition at all times. This includes the automatic transfer equipment and antenna system. The DCS should be advised immediately by radio of any serious aerophare difficulties that would jeopardize this service. We cannot stress the importance of this subject too much since recently several installations have operated improperly due to lack of simple maintenance.
TMC-T RELAY ADJUSTMENT
From the Ground Radio Shop, we have a note pertaining to chatter of the slow release relays. Improper adjustment of the spring contacts 1-2 and 6-7 on relay 24l, resulting in contacts 1-2 opening before contacts 6-7, causes the relays to fail to release after dialing. When contacts 6-7 open at the same time as, or slightly before, contacts 1-2, operation is normal.
Another item on the TMC-T appears to indicate that both Clare and American Automatic Electric Company slow release relays, and stepping switches, are used in the unit. The resistance of the relay solenoid coils manufactured by one company is not the same as in those made by the other company, though the relays serve the same functions* All relays in a unit should be manufactured by the same company.
