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section 4
service instructions


4.1 GENERAL

Included in this section are signal tracing procedures alignment and neutralization procedures, and voltage and resistance measurements. If any soldered parts are removed or replaced at terminals to which semiconductor diodes are connected, be sure to attach an alligator clip to the diode lead. This acts as a heat sink to protect the diode.

To remove the transceiver chassis from the cabinet, lift the lid and remove the two Phillips head screws located between the lid fasteners. .Remove the four feet and the screw located midway between the rear

   

feet. From the rear, push the chassis forward until the front panel protrudes from the cabinet about an inch. Grasp the front panel at the edges, and carefully slide the chassis out of the cabinet.

4.2 TRANSMITTER SIGNAL TRACING

Table 4-1 lists appropriate signal generator connection points and normal signal levels. Figure 4-1 shows location of adjustments. Before making measurements, set EMISS10N switch to USB, disable the power amplifier by disconnecting the jumper between J5 and J6, and disconnect the +800 -volt dc plate voltage


Table 4-1. Transmitter Signal Levels.
 
SIGNAL GENERATOR
CONNECTION POINT
BAND-SWITCH
POSITION
SIGNAL GENERATOR
FREQUENCY
SIGNAL GENERATOR
OUTPUT VOLTAGE
V8-2 (grid)
 
 
 
 
V7-1 (grid)
 
 
 
 
 
 
V6-2 (grid)
V5-2 (grid)
V4A-6 (grid)
3.8
7.2
14.2
21.4
28A
3.8
7.2
14.2
21.4
28A
28B, 28C 

14.2
4.2
14.2
3.9 MHz
7.3 MHz
14.3 MHz
21.5 MHz
28.6 MHz
3.9 MHz
7.3 MHz
14.3 MHz
21.5 MHz
28.6 MHz
According to crystal used
3.055 MHz
3.055 MHz
455 KHz
0.5 volt
0,41 volt
0.5 volt
0.2 volt
0.75 volt
40,000 microvolts
22,000 microvolts
43,000 microvolts
30,000 microvolts
32,000 microvolts
 
 
32,000 microvolts
62,000 microvolts
12,000 microvolts

For the following, disconnect the signal generator, remove J16 short, set EMISSION switch to TUNE, and adjust MIC GAIN for grid current threshold. Measure with ac vtvm or calibrated oscilloscope.

V3A-7 (cathode)
V3A-9 (grid)
V11-9 (grid)
any
any
any
*1750 Hz
*1750 Hz
*1750 Hz
0.014 volt
0.06 volt
2.8 volts

For the following, turn EMISSIONI switch to USB and connect audio oscillator to J11 through a 40-dB pad. Set MIC GAIN fully clockwise, and adjust audio oscillator output for pa grid current threshold.

V1A-9 (grid) or
J11 PHONE PATCH
Any 1500 Hz 35 millivolts through
a 40-Db pad

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