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Troubleshooting Guide
FM SECTION
1. Poor S/N ratio
a) Large ripple is contained in the +B circuit (ripples
with 20uV or less is negligeble).
b) LPF constant in the control circuit is improper.
c) 1C202 is faulty.
Note:
Improper
routing
of wire, etc.
affects S/N
ratio,
2. Poor sensitivity (white noise is intefered)
a) IC201 is faulty.
b) Adjustment incorrect.
AM MW (LW) SECTION
1, 1.0V adjustment cannot be made
at the lower edge
frequency.
a) OSC coil L109 (L111) is faulty.
2. 20V adjustment cannot be carried out at the higher
edge frequency.
a) OSC trimmer CT105 (CT106) is faulty.
3. Tracking error is too large.
a) Varicap diode at OSC
side and that at ANT side
do not match
each other in characteistics. (A set
of varicap diodes
(two) should
be replaced at a
time. Never replace each of them separately.)
b) Band edge voltage is not correctly preset (See a)).
c) Varicap diode is faulty (See a)).
d) Bar antenna coil is faulty.
CONTROLLER SECTION
1. Auto-stop does not work
a) Check if scanning stops automatically the instant
the Pin 17 of the Tuner
p-c board
is shorted
to
the chassis after pressing Up or Down button with
the Manual/Auto switch set at Auto.
The control circuit is normal if scanning stops.
2. Unrelated segments of the frequency dimly glows.
a) Zener diode D229 is faulty.
3. The frequency display cannot be tuned in.
a) CPU
program
of the controller
is out of order.
Unplug the power cord to reset and plug in again.
4, After Up/Down button is pressed while the Standby
switch
is turned off, the last channel is replaced by
the new frequency, when power is turned on.
a) Lock circuit is faulty.
&. When
the power
cord
is unplugged and plugged in
again, the last channel is not maintained.
a) Memory back-up circuit is faulty.
6. Waveform for FM does not appear on CRT.
a) Prescaler 1C201 and its related circuit is faulty.
b) FM OSC circuit is faulty.
c) FM LPF circuit is faulty.
d) IC202 faulty.
Guide de dépannage
SECTION MF
1. Rapport S/B défectueux
c) Le circuit 1C202 est défaillant.
rapport S/B.
a) Circuit 1C201 défaillant.
b) Reglage incorrect.
SECTION MA GO (OM)
i
quence de limite supérieure.
"erreur d'exploration est trop importante.
c) Le varactor est défaillant (voir a)).
d) La bobine de I'antenne barre est défaillante.
SECTION CONTROLEUR
1.
L'arrét automatique n'opére pas
lument faiblement.
a) La diode Zener D229 est défaillante.
a) Le circuit de verrouillage est défaillant.
du tube cathodique (CRT).
b) Le circuit de OSC MF est défaillant.
c) Le circuit de MF LPF est défaillant.
d) 1C202 est défaillant.
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