Table of Contents
Advertisement
I{A I NTENANCE
Remove
the eight screws
secur-
ing the
RF
shield.
Unsolder the antenna connector
and remove the trto retaining
screws.
Remove
the two
screws
in the
PA
transistor
Q253.
Turn the radio over and
remove
the hex screw Post,
washer
and
copper spacer from the stud of
Driver transistor
Q252.
Remove
the 9
sc
rews
securi
ng
the Tx-Rx board and carefullY
lift
up the board off of
the
i
nt
erconnec
t i
ons
Pi ns
.
To remove the interconnect/
mul
t
i-frequency
boa
rd
;
Remove
tbe toP
cover.
In multi-frequency units, t€-
move
the five screws
securing
the
RF
shield.
Remove
the 12 screws
securing
the board and carefullY lift
the board up to disconnect
the
interconrection pins.
PA
TRANSISTOR
REPLACEMENT
LBr:i1072
printed circuit board runs
because
part of the matching network is
included in the
base and
collecLor
runs.
Tri-m
the
new
translstor
leads (if
required) lo the lead length of
the removed transi stor.
The
1et
Ler rrcrr on the top of the
transistor
a
lso
indicates
the
col lector
(see Figure
3 for
t
ransistor lead identifica tion
)
.
Apply a
coa
t of
si
1
icon
grea
se
between the mounting surfaces of
the spacer and to both sides of
the insulator of
Q252
and
between
the mounting surfaces of
Q253
and
the heat sink and on both
ends
of
the spacer. Place the transistor
in the mounting hole.
Align
the
leads as shown on the Outline
Diagrarn. Then hold the body of
the transistor
and replace the
transistor
mounting
hardware,
using
modera
te
torque of
0.6
Newton meters (Nm) or 6 inch
pounds) for M2.5 screw size
and
1.0
Nm
(8 inch
pounds)
for the
hex
screw post.
A torque
wrench
must
be used for this adjustment
since
transistor
damage
can result
if
too little
or too
much
torque
1s
used.
Solder the leads to the printed
circuit
pattern.
Start al
the
inner edge of mounting hold
and
solder the remaining length of
transistor lead to the board.
Use
care not to use excessive
heat
that
causes
the printed wire
board
runs to Iift
up from the
board.
Check for
shorts
and solder
bridges.
7.
Replace Tx/Rx board and
reassemble
radio.
REMOVING }C
!
S
Removing ICrs
(and
a1I
other
soldered-in
components) can be easily
accomplished
by using a de-soldering tool
such as a
SOLDA
PULLTo
or equivalent.
To
remove
an IC, heat each lead separately
on
the solder side and
remove
the old solder
with the de-soldering tool.
5.
4.
7.
t
J.
I]RIVER
-AND
b.
Q253:
To replace
PA RF
transistors
Q252 and
1
.
Rernove
Tx/Rx
boa
rd
.
2.
Unsolder one
lead at a time with
a
50 watt soldering iron.
Use
a
scribe or X-actroo knife to
hold
the lead away from the Printed
circuit
board until
the solder
cool
s.
Lift
out the transistor,
and re-
move the old solder
from the
printed circuit
board with a
de-
sol
deri
ng tool such
a
s a
SOLDA
PULLTo. Special care should
be
taken to prevent
damage
to
the
WARNING
The stud
mounted
RF Power Transis-
tors
used
in the transmitter contain
Beryllium Oxide, a
TOXIC
substance.
If the ceramic or other
encaPsula-
tion is opened, crushed, broken
or
abraded, the dust
may
be
hazardous
i
f
inha led
.
Use care in rePlacing
transistors of this
tYPe.
CAUTION
Failure to solder the transistor
leads as directed may result in
the generation of RF loops that
could
damage
the transistor
or
may
cause low power
output.
11
Advertisement
Table of Contents
