JVC JL-F50 Service Manual page 14

8-(3) Chart 2. Platter rotates at high speed
( Platter rotates at a higher speed.
Does the
rotation stop
Yes Circuit is normal
when the base of X9
between X9 and
are shorted? Check preced-
ing parts of the
Circuit.
Does the rotation stop
when the collector of
X9 is earthed?
Collector and emitter of
X9 are shorted.
Replace XQ.
Erratic platten rotation
When the condensor C5
Is open
If the registor R10 or R100
is adjusted improperly.
The rotation accelerates
and the ripples across
resistor R14 increase.
Voltage changes from
40mV to 400mV.
Speed drift is so great that the
rotation stop when
the base of X10
Collector and emitter of
X10 are shorted.
Replace X10.
| JL-F50
Does the
rotation stop
when the base of
X12 is connected
to +18.0 line?
| Does the
Yes rotation stop Yes
when the base of
X11 is earthed?
Does the
is earthed?
No No
Check if collector and Check if collector
emitter of X11 are open. and emitter of X12
Check for incomplete are shorted.
soldering. If so, replace it.
Is the
resistor R16
disconnected? Is
DC voltage from 4 to
6V present at the
both ends of
R14.
If no voltage is present,
either C5 is shorted, or
the +pole of C5 is touch-
ing the +18.0 line.
8-(5) Chart 4. Weak starting and long rise time
Weak starting torque and long rise time
Starting torque is weak,
but a small push starts the
turntable, which then runs.
Fluctuation is
produced.
ls power voltage of about
18.5+0.8V present at emit-
ter of X101?
In the case of improper adjustment,
voltage changes to 120mV and re-
volution becomes incorrect.
Re-adjustment is required.
In the case of the proper adjustment,
* the voltage is 40mV.
This condition is produced
when one of the transistors
from X1 through X8 Is open.
The Zener diode D105 or
the transistor X101 are de-
dective.
platter rpm may be as high as
45 rpm when the speed select
switch is set to "'33".
When the diode D11 is shorted,
the speed fluctuates and rpm
increases by 5 to 6%.
Diode D11 inside
the motor is open.
Replace defective
parts.
No. 2411 <4 =
Collector and
emitter of X13
are shorted.
Replace tran-
sistor(s) if
defective.