TM 5-6115-332-14
P-8-614-14
TO 35C2-3-424-1
NOTE
Before any point to point checks can be
made, scrape ends of items being check-
ed to insure that a good electrical con-
tact can be made. Recoat with varnish
after repair or test.
(3) Locate CR5,
1N414 D10DE, measure
resistance,
reverse test leads and measure
resistance again. Acceptable limits are LOW
resistance of 9-11 OHMS one way, and more than
100,000 OHMS the other way. If LOW or HIGH
resistance is measured in both directions, remove
and replace CR5.
(4) Locate CR6,
1N5296/1N5297 Current
Regulating Diode and perform tests in paragraph
d., (3) above. If resistance is LOWER than 800
OHMS in both directions, locate Q1 2N2405
Transistor, remove and replace it. After replacing
Q1, measure the resistance of CR6. If readings are
still not within limits, remove CR6, then replace it.
(5) Locate Q2 2N3442 Power Transistor,
located on back of regulating housing. Remove two
(2) screws securing Q2 to the housing. Pull straight
from housing, being careful not to damage the
micro spacer beneath the body of Q2.
(6) Set the multimeter to RX 10,000 OHMS,
Resistance Test. Position Q2 2N3442 with the two
(2) pins of the device pointing toward individual,
line up the pins so they are in the lower half of the
device with the two (2) mounting holes at the top
and bottom. While in this position the pin on the
left hand side is the Emitter, the pin on the right
hand side is the base and case of the device, and is
the Collector. Test with the Black lead of the
multimeter on the transistor body and Red lead on
the LEFT pin, then the RIGHT hand pin of the tran-
sistor. There should not be any movement of
multimeter point. Reverse the leads and perform
same procedures. Readings should indicate no
movement of the multimeter pointer on Left hand
pin should read between 10,000 OHMS, to 20,000
OHMS on Right hand pin. LOW or HIGH
resistance on both pins as a result of the above two
checks, indicate either an open or shorted junction
within Q2, replace Q2. Replace Q2 along with the
mica insulator located between the transistor body
and the regulator housing.
CAUTION
Do not remove the white paste from the
micro spacer or regulator housing. If
this dielectric heat transfer paste is
removed, destruction of Q2 will occur.
(7) Connect the 30 OHM, 25 Watt resistor to
terminals 20 and 21 of TB1. Connect two (2) 12-18
AWG insulated wires to the 750 OHM Rheostat as
follows:
(a) First position Rheostat with shaft control
toward individual and three (3) terminal lugs in
back at 12:00 O’Clock position. Connect one (1)
wire to middle lug and one (1) wire to the right hand
lug. If the Rheostat has a jumper wire connected
across any two (2) terminals, remove the jumper
wire. Conenct the 750 OHM Rheostat to terminals
26 and 28 of TB1 on the Voltage Regulator. Turn
the shaft of the Rheostat clockwise to its maximum
rotation.
(b) Connect the 110-12060 HZ AC Voltage
Source to terminals 24 and 27 of TB1.
(c) Set the multimeter on 50 DC Volt range.
Test for 26-32 DC Volts between terminals 20 and
21 of TB1. Positive polarity on terminal 20, and
Negative polarity on terminal 21. Rotate shaft of
Rheostat counter clockwise to approximately
eighty (80) percent of rotation, somewhere in this
position the voltage at terminals 20 and 21 of TB1
should collapse to Zero volts. Rotate the shaft of
Rheostat clockwise until somewhere near eighty
(80) percent of rotation, the voltage should reap-
pear on terminals 20 and 21 to the 26-32 DC Volt
range. In the event that there is a pause longer
than two seconds before the voltage increases or
decreases when resetting of the Rheostat, then an
adjustment of R6 must be made.
(d) Locate R6 on the circuit board. By turn-
ing the adjustment screw of R6 counter clockwise,
the voltage will be on at terminals 20 and 21 of
TB1. By turning clockwise, the voltage will col-
lapse to Zero.
NOTE
There will not be an adjustment of R6 to
where the voltage at terminals 20 and 21
can be made to viny. Either the voltage
will be ON or OFF.
Change 3
7-4.1
