Pa Transistor Replacement; Disassembly Procedure (Top View) - GE MASTR II Maintenance Manual

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MAINTENANCE
BOTYOM
COVER
RETAINING
SCREW
Figure 5 - Disassembly Procedure
Top View
PA TRANSISTOR REPLACEMENT
WARNING
--------·------~
The stud mounted RF Power Transis-
tors used in the transmitter con-
tin Beryllium Oxide, a TOXIC sub-
stance. If the ceramic or other
encapsulation is opened, crushed,
broken or abraded, the dust may be
hazardous if inhaled. Use care in
replacing transistors of this type.
To replace the PA RF transistors:
1. Unsolder one lead at a time with a
50-Watt soldering iron. Use a scribe
to hold the lead away from the printed
circuit board until the solder cools.
2. Turn the transmitter over.
3. Hold the body of the transistor to pre-
vent it from turning. Remove the tran-
sistor hold-down nut and spring washer
through the hole in the heatsink with
an 11/32-inch nut-driver for Q201 and
Q202, and a 3/8-inch nut-driver for
POWER
LEADS
4.
5.
LBI-4896
Figure 6 - Disassembly Procedure
Bottom View
Q203, Lift out the transistor and
remove the old solder from the'printed
circuit board with a de-soldering tool
such as a SOLDA PULLT®, Special care
should be taken to prevent damage to
the printed circuit board runs.
Trim the new transistor leads (if
required) to the lead length of the
removed transistor. Cut the collector
lead at a 45° angle for future iden-
tification (see Figure 7). The let-
ter "C" on the top of the transistor
indicates the collector.
Apply a coating of silicon grease
around the transistor mounting surface
and place the transistor in the mount-'
ing hole, Align the leads as shown
in the Outline Diagram. Then hold
the body of the transistor and re-
place the holding-down nut and spring-
washer, using moderate torque (6.5
inch-pounds for Q201 and Q202, and
11 inch-pounds for Q203). A torque
wrench must be used for this adjust-
ment since transistor damage can
result if too little or too much torque
is used.
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