REPAIRS AND ALIGNMENT
Note: Before unsoldering parts, thoroughly remove
3-1. General Parts Replacement
the insulating varnish with varnish remover. Before
resoldering, brush the connections with flux cleaner.
Use rosin-core solder for all soldering on printed cir-
No special procedures are required for dis-
cuit boards, and recoat with insulating varnish (FSN
assembly and reassembly of the maintenance
kit except for the readout mechanism of the
e. Do not attempt to repair a printed circuit
radio set simulator. The procedures for disas-
board other than replacing attached parts and
sembly, reassembly, and adjustment of the
resoldering part connections.
readout mechanism are given in paragraph 3-
printed circuit board if more extensive dam-
3. General parts replacement techniques are
age has occurred.
given in a through h below.
f. Do not attempt to repair relays, trans-
a. Do not- disassemble any portions of the
formers, and potentiometers. Replace these
maintenance kit other than those necessary to
parts if they are defective.
g. If repairs on module extender cables W1
through W13 or the two cable adapters are
b. Before a part is removed, note the posi-
necessary, refer to figure 4-18 for point-to-
tion of the part, and label all leads where nec-
essary. Install replacement parts in the same
position as the original parts. This action is
h. Point-to-point wiring of the rigid module
especially important in the removal and re-
extenders is shown in figure 4-19. Refer to
placement of multisegment wafer switches. Ob-
figure 4-19 when replacing wires or connec-
serve polarity markings when replacing po-
tors to assure that the correct connections are
lorized capacitors and diodes.
c. When replacing parts in transistorized
3-2. Removal and Replacement
circuits, use a pencil-type soldering iron with
a maximum capacity of 25 watts. If the solder-
All modules, assemblies, and subassemblies
ing iron must be used with an ac source, use
are easily removed and replaced. Note the ca-
an isolating transformer between the iron and
bling connections when removing items so that
the line. Do not use a soldering gun; damag-
the proper connections can be made on replace-
ing voltages can be induced in the circuits.
d. Solder quickly when soldering transistor
3-3. Disassembly, Reassembly, and
or diode leads. When wiring permits, use a
Adjustment of Readout Mechanism
heat sink (such as long-nosed pliers) between
a. Disassembly (fig. 4-17)
the soldered joint and the transistor or diode.
(1) Loosen two setscrews (189) and re-
Use the same length and dress of leads as
move hundreds megacycle dial (188).