JVC MF-47L - Page 4

MF-47L/ML
Outline of Selection Circuit
Pre-set electronic
selection system is adopted. This
circuit consists of the following 4 part.
1.
2.
3.
Operation part.
Selection part which drives tuner after keeping the
touch-input signal in memory.
Indicator part which indicates the FM broadcast in
receiving.
Pre-set part to select the desired FM broadcasting
station previously.
Operation part
There are two kinds of the operation system:
senser system and switch system. Model FM-47ML uses
senser system of 2-pole type. (To touch 2 poles
simultaniously.)
Selection part
In this part, the touch input signal is kept in memory,
and pre-set voltage is given to the tuner driving circuit,
and also the output for indication of FM station is given
to the indicator circuit.
This part utilizes two pieces of IC (uPC 1009C) of
senser type which electronically select a station.
Indicator part
LED is used as for indicator of the FM station in
receiving. The output for indicator coming from the
selection part makes transistor switch to lighten
L.E.D.
Pre-set part
This part consists of 7 variable resistors for pre-setting.
Trouble shooting chart of FM pre-set.
All pre-set LED do not light.
(Defective) —>
U VES (Defect
Is the Function switch set at ‘““FM‘'?
NO ——— Set at ‘’FM”" position.
Pre-set L.E.D does not shift.
Is the sensor concerned with light-
ing L.E.D wet or dusty?
Remedy
Is’nt your finger too dry?
Are‘nt you physically
touching on moistened
floor or an object which
functions as an earth?
(ex. The fitting has earth
function.)
Is the +B1 & B2
voltage normal?
YES ——~ Check pre-set circuit board.
NO ——~>Check power source circuit.
YES Wp e thee dust or moisture enough.
1 Moisten your finger and try it.
YES—> 2 Put on slippers.
Keep your hand off the earth
object.
Tuning is slipping off though
Pre-setting was once made.
Does not change room temperature
greatly?
YES
Re-adjustment is needed.
NO Is‘nt the tuning knob operated? NO ——_» Check the pre-set or tuner
circuit board.
Caution: In case dusty oil was stuck on the pre-set circuit board, receiving frequency may vary from one of pre-set state.
No. 7011
Please be mind on this point when servicing.
NO ——— Check the pre-set circuit board.