Model 683C Section IV
Table 4-2 cont?d
Table 4-2. Troubleshooting Procedure (Sheet 4 of 4)
SECTION IV
LOW POWER OUTPUT AND/OR EXCESSIVE POWER SPREAD
Step 1. Reference Anode Circuit. 2) Replace bwo tube; refer to paragraph 4-13.
B. Excessive Power Spread.
A. Low Power. Connect an oscilloscope to the output of
cathode follower V303B and observe waveform.
1) Adjust dc level adj. R332 to obtain minimum of Vary segment 1, 2, 3, 4 adjusts. Each segment
30 milliwatts at low power point. See paragraph should vary as its adjustment is varied. If not,
4-16 and calibrate rf leveler circuit. possible trouble: CR302, CR303, CR304.
SECTION V
AMPLITUDE MODULATION
A. Set the SWEEP SELECTOR to OFF. C. Rotate AMPL. MOD. SELECTOR to INT.;
no square-wave output. Possible trouble:
B. Rotate MOD. SELECTOR to all three modu-
V301, C302, S301.
lating positions. INT., PULSE and EXT.,
applying an external signal where appropriate. If
there is no modulation output for all positions of
the AMPL. MOD. SELECTOR, possible trouble: D. No PULSE modulation, all other modulation
CR301, V301. Refer to paragraph 4-15 and cali- positions operating normally. Possible
brate circuit. trouble: S301.
0 1130- I |
ACEC
