f. Locate VR3 and apply the 110-120 Voltage
Source on terminals 24 and 27 of TB1. Check the
voltage across VR3. This is a 4.7 Volt Zener diode.
Remove VR3 and replace if the voltage is higher
than 4.7 Volts. If no voltage can be detected across
VR3, located R3, 1K OHM resistor. Check the
voltage at R3 to VR2 junction. There should be a
Negative 14 DC Volts present with respect to F ter-
minal on TB1. If Negative 14 DC Volts present
with respect to F terminal on TB1. If Negative 14
Volts is present and there is still no voltage across
VR3, remove and replace VR3.
g. In the event that none of the above checks and
replacement of components cause the regulator to
perform in acceptable limits, then AR1 is defective
and needs to be replaced.
Extreme care must be used while remov-
ing AR1 from the circuit board.
There are seven (7) connecting pins on the body of
AR1, locate the two (2) pins on one side and apply
the tip of the soldering iron alternately to both
pins while prying up the body of AR1 with a small
flat tip screwdriver. Once one side of AR1 is free,
repeat the same procedure on the remaining pins
and again pry upward until AR 1 is free of the cir-
While replacing AR1, it is good practice
to clean the circuit paths of solder where
the seven (7) pins of AR1 protrudes
through the circuit board.
h. Refer to the schematic diagrams for circuit
review and analysis. If replacement parts are re-
quired, order by part number and manufacturers
code as indicated on fold-outs FO5 and FO6,
located in the back of the manual.
i. After all tests, repair or replacement of parts
have been accomplished, recoat using Varnish
(MIL-I-24092, Type M, Class 155).