TM 11-5840-208-30-1
(3) Adjust the LO ADJUST attenuator in the receiver compartment until the crystal current meter reading is
between 2 and 3.
STC Adjustment. The three adjustment controls for the STC assembly are on the top portion of the chassis.
b.
These controls are preset at the factory and ordinarily require no adjustment. The interrelationship between STC
sensitivity adjust R4708 and time constant adjust R4712 is extremely critical. These adjustments should be referred to a
higher echelon. The adjustment procedure for STC amplitude adjust R4714 is given below.
(1) Loosen the two knurled thumbscrews on the front flange of the STC chassis and slide the chassis part way
out.
(2) Disconnect W1 508 from J4702.
(3) Connect an oscilloscope to J4702; use the coaxial cable supplied with the oscilloscope.
(4) Adjust the oscilloscope for a presentation of the STC sawtooth waveform.
(5) Adjust R4714 until the amplitude on the waveform is 6 volts peak to peak.
(6) Disconnect the oscilloscope from J4702 and reconnect WI 508 to the same jack.
(7) Slide the chassis back into position and tighten the thumbscrews.
Range Markers. If the amplitude of the range markers is not satisfactory, adjust R1333 on the AFC assembly
c.
until sufficient amplitude is obtained.
5-5. TRANSMITTER ADJUSTMENTS
a.
General. The transmitter operates on a fixed frequency and requires no tuning. However, certain control circuit
adjustments are necessary due to component aging or replacement.
Warning: Do not reach into the transmitter compartment during the following adjustments--voltage in excess of 26,000
volts is present. Avoid touching terminal boards TB 1101 and TB 1102 mounted on the transmitter compartment door.
These boards have potentials up to 300 volts. Under no circumstances should the following terminals be disconnected
while the transmitter is on, nor should the transmitter be turned on while they are disconnected: TB 1101, pins 5, 10; TB
1102, pins 1, 2. The voltage at these terminals is normally low; however, if they are opened while the transmitter is on, the
voltage may rise as high as 30 kilovolts.
Thyratron Switch Adjustments.
b.
(1)
Open the transmitter compartment door and close shorting switches S1103, S1105, and S1107.
Caution: Do not adjust T1107 while the transmitter is on. After making any adjustment of Tl107, wait at
least 3 minutes before turning the transmitter on. This permits the hydrogen pressure in the
thyratron to stabilize at the new setting.
(2)
Set T1107 at midposition. While observing voltmeter M1101, adjust Rllll into each limit. Adjust RI ll so that the
voltmeter reading is halfway between the high and low readings just obtained.
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