TM 55-4920-399-13&P
Display over-range regard-
LO Z shorted to Hi Z
(1) Check cables for leakage inside
(1) Internal
measured.
unit to LO Z, Hi Z, and LO Z
Comp.
(2) Check Cable Assemblies with
(2) External
megohmmeter for leakage.
(1) Remove all external cables.
Hi Z shorted to ground
Displays zero regardless
Check HI Z - GND setting of
of input.
perly (R=00), re-attach cables
and remeasure. If it still reads
properly, check for presence of
LO Z
(1) Check for presence of LO Z us-
LO Z shorted to ground.
ing an AC meter or scope bet-
ween LO Z and GND with
T/U/COMP switch in T/U
position; or Lo Z COMP jack to
GND, T/U/COMP switch in
COMP position.
(2) Check 1.02 - GND and LOZ
COMP - GND with megohm-
meter with cables attached and
then unattached. If it checks
properly (R =00), check LO Z
Filter Board A5 (See board
checkout procedure).
(1) Remove cables, check read-
(1) Internal leakage
i n g s , on a l l p o s i t i o n s o f
reading.
MEGOHMMETER switch. It
should read 00; if it doesn't,
there is excessive moisture in-
side unit causing leakage. Dry
with warm or compressed air.
(2) Attach all cables, measure all
(2) External leakage
positions of the MEGOHM-
METER switch. If it reads less
than 00, leakage is in cables.
If it reads 00, check Megohm-
meter Board A2.
3-3