Table 6-2. Troubleshooting

TM 11-6625-542-14-1

(2) Remove diode which couples defective

(4) If the input signal to the multivibrator

stage to following stages. If the defective stage then

registers on the oscilloscope but no signal appears at the

functions normally, the trouble is probably due to loading

output, measure the voltage at multivibrator plate which

by the stages that follow.

connects directly to the input diode plate. The voltage

reading should be +225 volts. The plate voltage of the

NOTE

other half of the tube should read + 100 volts. The grid

Before replacing any components, isolate the

voltage on the first half of the tube should read

trouble by checking the multivibrator with an

approximately --6 to --8 volts.

oscilloscope and voltmeter.

Multiplier Checks. The multiplier circuits may

(3)

To check multivibrator, check the

become faulty due to tube failure. These troubles may

incoming signal at the grid on one-half of the tube and

be corrected by replacing the faulty tube. Readjustments

the output signal. An oscilloscope is used for this test. If

are sometimes necessary due to aging of components

desired signals are present and pin voltages are correct,

and to variations in characteristics of replacement parts.

check for signals at the output cathode follower stage. If

Refer to section III for adjustments.

no signal appears on the cathode, check through switch

S710 to the MARKER OUT connector.

Table 6-2. Troubleshooting

Malfunction

Probable cause

Corrective action

Improper or loss of time-marks when 1

Defective tube V262, V265, V273

Check and replace defective tube.

MICROSECONDS button depressed.

2. Improper or loss of time-marks when 5

Defective tube V262, V265, V273, V502,

Check and replace defective tube.

MICROSECONDS button is depressed.

V503, or V533.

3. Improper or loss of time-marks when 10

Defective tube V502, V503, V533, V522,

Check and replace defective tube.

MICROSECONDS button is depressed.

V543, or V535

4. Improper or loss of time-marks when 50

Defective tube V522, V543, V535, V552,

Check and replace defective tube.

MICROSECONDS button is depressed.

V553, or V583.

5. Improper or loss of time-marks when

Defective tube V552, V553, V533, V572,

Check and replace defective tube.

100 MICROSECONDS button is

V593, or V585.

depressed.

6. Improper or loss of time-marks when

Defective tube V572, V593, V585, V402,

Check and replace defective tube.

500 MICROSECONDS button is

V403, or V433.

depressed

7. Improper or loss of time-marks when 1

Defective tube V402, V403, V433, V422,

Check and replace defective tube.

MILLISECONDS button is depressed.

V443, or V435.

8. Improper or loss of time-marks when 5

Defective tube V422, V443, 435, V452,

Check and replace defective tube.

MILLISECONDS button is depressed.

V453, or V483.

9. Improper or loss of time-marks when 10

Defective tube V452, V453, V483, V472,

Check and replace defective tube.

MILLISECONDS button is depressed.

V493, or V485.

10. Improper or loss of time-marks when 50

Defective tube V472, V493, V485, V302,

Check and replace defective tube.

MILLISECONDS button is depressed

V303, or V333.

11. Improper or loss of time-marks when

Defective tube V302, V303, V333, V322,

Check and replace defective tube.

100MILLISECONDSbutton is

V343, or V335.

depressed.

12. Improper or loss of time-marks when

Defective tube V322, V343, V335, V352,

Check and replace defective tube.

500MILLISECONDSbutton is

V353, or V383.

depressed.

13. Improper or loss of time-marks when 1

Defective tube V352, V353, V383, V393,

Check and replace defective tube.

SECONDS button is depressed.

V385, or V372.

14. Improper or loss of time-marks when 5

Defective tube V393, V385, V372.

SECONDS button is depressed.

15. Improper or loss of trigger pulses when

Defective tube V262, V273, V265, V502,

Check and replace defective tube.

100KC-10SCS button is depressed.

V503, or V533.

16. Improper or loss of trigger pulses when

Defective tube V522, V543, V535, V552,

Check and replace defective tube.

10 KC-100 S button is depressed.

V553, or V583.

17. Improper or loss of trigger pulses when

Defective tube V572, V593, V585, V402,

Check and replace defective tube.

1KC-lMS button is depressed.

V403, or V433.

18. Improper or loss of trigger pulses when

Defective tube V422, V443, V435, V452,

Check and replace defective tube.

100 - lOMS button is depressed.

V453, or V483.

19. Improper or loss of trigger pulses when

Defective tube V472, V493, V485, V302,

Check and replace defective tube.

10S-lOOMS button is depressed.

V303, or V333.

20. Improper or loss of trigger pulses when

Defective tube V322, V343, V335, V352,

Check and replace defective tube.

1S-lSEC button is depressed.

V353, or V383.

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