Connect the flexible lead from condenser C21B to turns of coil L6B as
fol lows : For frequencies from 500 to 750 ki locycles the condenser tap shall be
connected to turn 34 ; for freq uencies from 750 to 1,500 kilocycles the condenser
tap shall be connected to twice th e n umber of turns to which the tuning tap of
L6B is connected. For example, if the tuning tap is on turn 8, then the con-
denser tap shall be connected to turn 16.
·
�
'
The triple-pole double-th row switch D7B located to the right of load resist
ance Rl 7
B
and below tuning condenser C7B, should be in the position that con
nects the h igh current thermocouple H6. 1B in the load resistance circu it. The
" H EATE R" of thermocou ple H 6 . 1 B should be short-circuited with short-circuit
ing- stra p D8B during th e prel iminary tuning of the transmitter. The short
circuit stra p is removed when th e transmitter is tuned.
In
the lower left-h and corner and to the rear of the Amplifier Unit there are
two sets of taps from potentiometer R5B. Each set of taps is marked " l , 2, 3,
4" corresponding to the classification numbers of the No. 212-D Vacu um Tubes.
The flexible lead on the terminal board marked "MODULATOR TUBE" should
be connected to the tap number which corresponds to the classification number
etched on the modulator tube. The flexible lead on the terminal board marked
"THI RD AMPLIFIER TUBE " should be connected to the tap number which
corresponds with the classification number etched on the third amplifier t ube.
The field rheostat controls located on the front of the ampl ifier panel sh ould
be turned in a clockwise direction for minimum generator voltage. The "PLATE
VOLTAGE" switch D3B should be "OFF." The water inlet and outlet valves
controlled from the inside of the Amplifier Uni t and located in front of the two
No. 212-D Vacuum Tubes should be in the "ON" position. The motor-generator
sets are started by operating the top button of the "MASTER CONTROL"
switch D2B. This starts both motor-generator sets and at the same time the
pump motor thereby starting th e circulation of the cooling water. The water
pressure sh ould be adj usted in accordance with the procedure outlined on
pages 56 to 59 i nclusive.
The control of the field rheostat in the center of the amplifier panel marked
"250-VOLT GENERATOR" should be adj usted until meter M12B marked
"GRID VOLTAGE" indicates 250 volts. This voltage is necessary to close relays
S4B and S5B . Relay S4B is closed through operation of switch D3B, and relays
S2B and S l B . Relay S l B operates when the filament voltage attains a valu e of
22 volts. Relay S5B operates th rough the contacts of water flow relay S6B.
Relay S6B is operated by the differential pressure from the Venturi T ube.
The filament voltage should be adj u sted by field rheostat control marked
"24-VOLT GENERATOR," u ntil meter M lOB marked "FILAM E NT VOLT
AGE" indicates 22 volts.
After the relays have operated it is possible to close the field circuit of the
high voltage generators by pushing the top button of the "PLATE VOLTAGE"
switch D3B. The plate voltage should be adjusted by the rheostat control marked
"4000-VOLT GENE RATORS" until meter M l l B marked "PLATE VOLTAGE''
indicates 4,000 volts.
[ 42 ]
