Trouble Shooting - JVC QL-F300 Service Manual

13. Trouble Shooting
The turntable rotates at high speed.
The turntable does not rotate.
Does 22-23
V DC appear at the
emitter of Q801?
(The tonearm should
be out of the
Q801 or Q802 is
defective, or D802 or
SW801 is shorted?
Replace it.
Does around 30-40
V DC appear at the
collector of Q801?
Does a sinewave of
0.3 Vp-p appear
at TP-3?
Does the turntabie
stop by grounding
TP.4?
D801 is discon
nected, or the
transformer is open.
IC1 is defective. Or,
check C7, R16 and
R15 for disconnec-
tion
Does the
turntable stop by
shoting between the
base and emitter
of 9?
Does 22-23 Vv
'appear between powor
supply line sockets 1
and 2 on the motor
board ?
Q10 is defective.
Replace it
Check the wires tor
disconnection and the
sockets for
looseness. If any 1s
defective, replace it
When the turntable
stops by connecting
the emitters of Q5
and Q6 to -12V,
Q9 is defective
between TP-1 and
TP-2 when observed
on an oscilloscope?
IC1 on the MC9548
motor board 1s defec-
tive. Check Q12 and
Q13.
is the voltage
at TP-4 around 0.3 V?
IC1 is defective. Or,
check R18 for
disconnection, etc.
No
The turntable RPM is abnormal
Does the turntable
rotate by shorting
between the collector
and emitter of
Q10?
Q10 is defective.
Replace it Check the motor
FG pattern, etc.
Check the
following and replace
the defective parts
the turntable
rotate by shorting
between the
collector and
emitter of Q9?
R3, R8, RS or RG is
disconnected. Or,
check the Hall collec-
tor and emitter of
ag?
QS9 is defective.
Or, check C1 for
short, etc.
C6, C7, R13, R14
are shorted
or opened?
QL-F300
_17— No. 2650