INDICATOR b. Wiring defective ------- b. Perform continuity checks
to locate defect, and re-
does not extinguish
place or repair as re-
and coupler does not
stop tuning when FR
Wiring to Z1 or to S3 de- Perform continuity checks to
fective Z1 defective.
locate defects in wiring.
Repair or replace as re-
quired. If no defects are
located in wiring, replace
u r e m e n t s are presented in the chart in (2)
a. T h e t u n i n g s i g n a l f r o m t h e a n t e n n a
below. Use these measurements and the
coupler may be monitored at MOTOR PULS-
s c h e m a t i c diagram (fig. 53) to isolate trou-
ING SIGNAL jack J1 of the test set with an
T h e normal waveform obtained
Caution: When measuring voltages, use
tape or sleeving (spaghetti) to insulate the
b. Since the antenna coupler used
entire test prod, except for the extreme tip. A
the test set is known to be working properly,
momentary short circuit can ruin a transistor.
a departure from the normal waveform in-
(1) The voltage readings will always be
dicates that trouble exists in the test set. Check
obtained as given in (a) through (d) b e l o w .
a l l wiring between the point at which the
(a) Make voltage measurements using
waveform is observed and the antenna coupler.
Multimeter ME-26B/U or equivalent.
(b) M a k e a l l v o l t a g e m e a s u r e m e n t s
2-7. Isolating Troubles
with respect to chassis ground.
a. General. Once a trouble has been localized
(c) M a k e a l l v o l t a g e m e a s u r e m e n t s
to a functional circuit in the test set, it may
with dc power (28 volts) applied. Do not c o n -
be necessary to perform further tests to isolate
nect any other test equipment such as the fm
the trouble to a particular component. When a
trouble has been localized to a functional cir-
(d) M a k e a l l v o l t a g e m e a s u r e m e n t s
cuit, review the principles of operation of that
with the MANUAL TUNE switch and the
METER FUNCTION switch set to OFF.
form resistance and continuity checks ( b
( 2 ) Resistance measurements are made
b e l o w ) and voltage resistance measurements
with power disconnected from the test set. Use
(c below) as required.
Caution: Do not make resistance and con-
ments with respect to chassis ground.
tinuity checks with power applied to the test
set. DO not make any measurements that would
b. Resistance and Continuity Checks. W h e n -
e v e r required, perform resistance and con-
t i n u i t y checks on resistors, capacitors, and
wiring with a multimeter.
c. Voltage and Resistance Measurements.
urements are taken at the emitters, bases, and
collectors of Q1, Q2, and Q3. The normal meas-