Transmitter Servicing Course

With the equipment ready for operation, the main line switch (S-831), the EMERGENCY SWITCH (S-12) and the main line contactor contacts K-831B all are closed. (1) The keying relay main contacts (K-1C) ground the center tap of the MO filament secondary of T-1 to complete the DC return path to the filament and allow the MO to oscillate. (1) Conta

cts K-2B connect the AC supply to the compensator transformer (T-3) to heat the compensating capacitor (C-62). This capacitor is a bi-metallic device which compensates for the changes in MD circuit capacity due to the expansion of tube elements under key-down conditions. (b) If the temperature in the compartment is below 60 ° C, the thermostat (S-13) contacts are open, preventing the thermostat relay (K-20) from being energized. The heating element (R-26) is energized through the normally closed contacts (K-20B) of the thermostat relay. (c) When the temperature in the compartment reaches 60 ° C, the mercury column of the thermostat (S-13) completes the circuit to the thermostat relay coil (K-20A). (e) If either S-13 or K-20 fail to operate, the temperature protection switch (bi-metallic Spencer Disk S-11) will turn the heating element (R-26) off and on within the limits of 71 ° and 55 ° C. 2. GENERAL CIRCUIT CONDITIONS: An electron coupled circuit, Class C, with plate circuit always tuned to the second harmonic of the grid - screen grid circuit. (1) Coarse tuning in 8 steps with MASTER OSCILLATOR RANGE MC control (S-1). Switch interlock contacts S-1C break the keying circuit while S-1A and B are between steps. (b) MO CALIBRATION CORRECTOR capacitor (C-61) should be set half open before the transmitter is calibrated. When MO tubes or parts are changed, C-61 may be adjusted to make the MO frequency correspond to the...

Leave Comment

characters left:

New Circuits