Cessna 1969-1976 172 Series Service Manual page 284

PROBABLE CAUSE
Low battery voltage.
Faulty transmitter.
TROUBLE
*POWER LOW
Faulty co-axial
antenna cable.
*This test should be carried out with the co-axial cable provided with your unit.
SHOP N O T E S :
REMEDY
1. Set toggle switch to off.
2. Remove plastic plug from the remote jack
and by means of a Switchcraft #750 jackplug,
connect
a
Simpson 260 model voltmeter and
measure voltage. If the battery-pack voltage
on the 6-cell magnesium battery pack t r a n s -
mitter is 10.8 volts or less, and on the 4-cell
lithium battery pack transmitters is 11.2 volts
or less, the battery pack is below specification.
3. If the battery-pack voltage meets the
specifications in step 2, the battery-pack
is 0. K. If the battery is 0. K.
,
check the
transmitter a s follows:
a. Remove the voltmeter.
b.
By means of a switchcraft 750 jackplug
and 3 inch maximum long leads, connect
a
Simpson Model 1223 ammeter to the jack.
the ammeter current drain. If the current
-
drain is i n the 85-100 ma range, the
transmitter
or
the co-axial cable is faulty.
c. Set the toggle switch to ON and observe
4. Check co-axial antenna cable for high
resistance joints. If this is found to be
the case, the cable should be replaced.
16-36 Change 3