Pa Transistor Replacement - GE MASTR II Maintenance Manual

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MAINTENANCE
LBI-4898
Figure 5 - Disassembly Procedure-Top View
To remove the PA assembly:
1.
2.
Remove the PA
top~ver
and unplug the
exciter/PA cable B ,
t~antenna,
receiver and PTT c les
~·
Remove the four side-rail screws
~
,
and unsolder the power cables from the
bottom of the PA assembly if desired.
To remove the PA board:
1.
2.
3.
4.
Remove the PA top cover and unplug the
exciter/PA cable ~ •
Unsolder the two
feedthro~
coils
~
and the thermistor leads ~ •
Remove the PA transistor hold-down nuts
and spring washers on the bottom of the
PA assembly.
R~ve
the four PA board mounting screws
\2) ,
t~five
screws in the filter
casting H , and the retaining screw
in Q210 , and lift the board out.
Figure 6 - Disassembly Procedure-Bottom View
PA TRANSISTOR REPLACEMENT
\"'ARNING - - - - - - - - . . . . . . ,
The stud mounted RF Power Transistors
used in the transmitter contain
lium Oxide, a TOXIC substance.
ceramic or other encapsulation is
opened, crushed, broken or ab·::-aded,
the dust may be hazardous if inhaled.
Use care in replacing transistors of
this type.
To replace the PA RF transistors:
1.
2.
3.
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,
Turn the transmitter over.
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. 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.
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