TM 9-6625-1753-14
Table 5-4. Troubleshooting Delaying Sweep Plug-in Type 74-13A
Malfunction
Probable cause
Corrective action
CRT screen is blank.
Open interlock circuit because the
Reinsert the unit, making sure
the
unit connector isn't plugged in the
connectors are properly mated.
main frame connector properly.
Defective unblanking amplifier circuit.
Check Q8401, Q8402, Q8403, Q8404,
Q8405
and
their
associated
components; replace the defective
transistor or component (fig. 5-12).
Measure the voltages as shown on the
functional schematic to help isolate the
defective stage and component.
Defective delayed-sweep gate or
Check Q8106, Q8107, or Q8206, Q8207
normal-sweep gate multivibrator.
and their associated components;
replace the defective transistor or
component (fig. 5-11).
No trigger output from differentiating
Check Q8101 or Q8202 and its associated
amplifier (shaper) Q8101 or Q8202.
components; replace the defective
transistor or component (fig. 5-11).
Check trigger amplifier circuit V8201,
V8202 (normal) and their associated
components including tunnel diode
CR8201; replace the defective tube or
component (fig. 5-12).
Check trigger amplifier circuit V8101,
V8102 (delayed) and their associated
components including tunnel diode
CR8101; replace the defective tube or
component (fig. 5-12).
TRIG-STROBE,
TRIG-DLY'D,
or
Check Q8001 and Q8002 and their
ARM-STROBE
sweep
modes:
associated components; replace the
Defective stage in the strobe circuit.
defective transistor or component (fig.
TRIG-STROBE,
TRIG-DLY'D,
or
Check Q8601, Q8602, Q8603, and Q8604
ARM-STROBE
sweep
modes:
and their associated components;
Defective stage in the delay trigger
replace the defective transistor or
pick-off circuit.
component (fig. 5-12).
Erratic triggering or no triggering at
Defective trigger amplifier or trigger
Check trigger amplifier V8201, V8202
any position of the SLOPE switch.
shaper stage.
(normal) or trigger amplifier Q8101,
V8102 (delayed) and their associated
components; replace the defective
transistor or component. Check trigger
shaper circuits Q8202 (normal) and
Q8101 (delayed) and their associated
components; replace the defective
transistor or component (fig. 5-12).
Figure 5-9. Dual-trace plug-in, right side view showing transistors.
5-7
