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L8r31072
MAINTENANCE
o252
025
r
NARROW
LEAD
IS
COLLECTOR
NARROW LEAD
IS
COLLECTOR
M2.
5
XB---=-
SC
REW
S
RC4?75
.t
I
'I
Figure 3 -
Q251
An
a
I
ternate
method is
to use
a
special soldering tip that heats ali of
the
pins
simul taneously.
TEST
AND
TROUBLESHOOTING
PROCEDURES
Maintenance
of radio is facilitated
by
use of the Troubleshooting Charts
and
servicing techniques unique to this radio.
The
Troubleshoot
ing Chart is designed to
lead you rapidly to the defective
component
or circuit.
Typical voltage readings
are
provided on the
Schematie Diagram
for
your
reference
when
troubleshooting.
Troubleshooting charts are provided
for
most major prob'lems
that might arise in
the
Transmi
tter/Receiver
section of the
radio.
SFRVIClNG
TECHNIQUES
The
high
cl.ensi
ty plug-in desigr of
the
modular radio lends itself
well to rapid
jsolation
of rpalfunctions in the voltage
and signal
paths.
A majority
of the
Lead
Identification
signals
and voltages pass through
the
connectors on the
IOC
board.
To isolate a signal or voltage path to
determine loading effects,
loca
te short
circuits,
ete. carefully insert an insulat-
or (plastic
wand, toothpick) between
the
appropriate pins of the related Molex
con-
nector to create an
open
circuit.
Signals
paths that
may
be isolated include:
Volume
SQ
HI, filtered
volume squelch
HI,
PTT,
Rx
II{UTE
,
a
nd
SPKR
HI
.
TEST
POINTS
RF Detector probes for the
recei-ver
section are available for alignment pur-
poses and to monitor the lst
receiver
injection at
TP401
and
the
2nd
IF at
TP501.
An RF signal probe also is available to
monitor the transmitter
frequency.
Seven test points are provided al
eritical
circuit
locations
to monitor
operation.
They
are as follows:
TRANSI',f
ITTER
Tp201
Al{pL
1
(Q201)
Emitter
Voltage
'TP2O2
TRIPLER
(Q202) Base Voltage
TP203
AMPL
3
(Q204)
Relative
Output
TP251
AI{PL
4
(Q251
)
Rela
t
i
ve
Out
put
RECEIVER
TP351 Tripler Output -
Q351
TP401 Receiver 1st oscitlator
injection
TP501 455 kHz
IF
12
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