TM 11-6625-1559-12
avoid further damage. Inspect the following for
c. Remove dust or dirt from plugs and jacks
obvious defects:
with a brush.
a. The seating of all tubes in their sockets.
Caution: Do not press on meter face
b. Wiring connections on the terminal boards.
(glass) when cleaning; the meter may become
c. Wiring connections to the switches and
damaged.
meters on the front panel.
d. Proper turning of
the gears on
the tuning
d. Clean the front panel, meters, and control
dial shaft assembly.
knobs; use a soft, clean cloth. If necessary,
dampen the cloth with water; mild soap may be
used for more effective cleaning.
4-13. General Troubleshooting Information
4-11. Touchup Painting Instructions
Troubleshooting this equipment is based upon
the operational checks in the daily preventive
Remove rust and corrosion from metal surfaces
by lightly sanding them with fine sandpaper.
Proceed through the items until an abnormal con-
Brush two thin coats of paint on the bare metal
dition or result is observed. When an abnormal
to protect it from further corrosion. Refer to the
condition or result is observed, note the trouble
applicable cleaning and refinishing practices spe-
and turn to the corresponding trouble in the
cified in TB SIG 364.
Caution: Do not use steel wool. Minute par-
checks and corrective actions indicated in the
ticles of steel wool frequently enter the case
troubleshooting chart. If the corrective measures
and cause harmful internal electrical shorting
indicated do not result in correction of the trou-
or grounding of circuits.
ble, higher category maintenance is required.
formation and step-by-step instructions for per-
forming equipment tests and adjustments to be
Before operating the sweep generator, inspect it.
used during the troubleshooting procedures.
Inspection will save repair time and may also
4-14. Troubleshooting Chart
Item
No.
Trouble symptoms
Probable trouble
Checks and corrective measures
1- - - -
T r a c e cannot be balanced
Q501 and Q502; replace as
a m p l i f i e r and marker amplifier
subassembly.
necessary.
Check tube V502; replace aa
2 -- - -
Dc level shift in oscillo-
m a r k e r amplifier subassembly.
scope screen.
a. Insufficient warmup time -----------
a. Allow at least 30 minutes
3- - - -
I n s u f f i c i e n t sweep
warmup time.
width.
b. A d j u s t S W E E D W I D T H
b. Improper setting of SWEEP
control to proper setting.
WIDTH control.
c. R e a d j u s t W O B B D R I V E L I M I T
c. Improper adjustment of WOBB
control for proper sweep width.
D R I V E LIMIT control.
a . D e f e c t i v e f u s e - - - - - - - - - - - - - - - - - - - - a. Check ac line fuse F1, B+ fuse
4- - - -
N o output on either
F2, and B- fuse F3; replace
u h f or vhf.
a s necessary (para 3-16).
Note. A defective fuse usually
indicates some other trouble. If
replaced fuses blow, higher mainte-
nance category repair is required.
b. Check tubes V301, V302, V303,
b. Defective tube in ALC sub-
assembly.
and V304; replace as necessary
a. Defective 5-MHz crystal ----------- a. Replace 5-MHz crystal V401.
5 -----
No markers on oscillo-
s c o p e pattern.
b. Check tube V401; replace as
subassembly.