(5) Apply a coating of Dow Corning
of the capacitors.
Heat Sink Compound No. 340 to
the mating flat surfaces on the heat
sink only and replace the diode with
2-7. General Parts Replacement
one of the same type. Install the
mounting hardware and torque to 30
All power supply parts, except diode recti-
u s e the
fiers, can be reached and replaced easily
wrench and torsion wrench.
without special procedures. The six diode
(6) Secure the pigtail lug of the diode
rectifiers must be replaced in accordance with
and the pigtail of the capacitor to
the specialized procedure given in paragraph
the bus bar on the heat sink; use
the hardware previously removed.
location of all parts. Connect replaced items
according to the schematic diagram (fig. 4-
of Variable Resistors
R1 and R2
a. With no load connected to the power
of Diode Rectifiers
supply and VOLTAGE ADJUST switch S2
a. The following chart lists the tools re-
set to NOM. set the circuit breaker switch
quired to replace the diode rectifier in the
to POWER ON.
b. Check to see that DIRECT CURRENT
VOLTS meter indicates 28.5 volts. If the in-
dication is not 28.5 volts, set the circuit break-
er switch to off and perform the procedures
in c through h below.
Warning: Do not touch the interior com-
ponents of the power supply unless the circuit
b. The six diode rectifiers are mounted on a
breaker switch is set to the off (down) posi-
is removed, the replacement diode must be of
c. Remove the top left side panel of the
the same type and mounted with the same ori-
power supply to gain access to resistors R1
entation as the removed part. Diodes CR1,
CR2, and CR3 are type 1N4587; diodes
CR4, CR5, and CR6 are type 1N4587R.
d. Loosen the sliding contacts on resistors
c. Replace any diode rectifier as follows:
R1 and R2.
(1) Before proceeding, make sure that the
e. Reposition the sliding contacts slightly.
circuit breaker switch is in the off
f. Set the circuit breaker switch to POWER
(down) position and that the input
ON and check to see whether DIRECT CUR-
power cable is disconnected from the
RENT VOLTS meter M2 indicates 28.5 volts.
(2) Remove the hardware that secures the
g. Repeat the procedures in e and f above
diode pigtail and capacitor pigtail to
until DIRECT CURRENT VOLTS meter in-
the bus bar on the heat sink. Do not
dicates 28.5 volts; always turn the power sup-
ply off before adjusting resistor sliding con-
(3) Make note of the diode type; diode
1N4587 is color-coded white and
h. Set the circuit breaker switch to the off
diode 1N4587R is color-coded violet.
position. Tighten the sliding contacts on re-
(4) Remove a defective diode by re-
sistors R1 and R2; replace top left panel of
moving the nut and lockwasher that
the power supply.
secure the diode to the bus bar.