Technics SL-Q303 Service Manual

LAs
SL-Q303
m TROUBLE SHOOTING GUIDE
1. No rotation
| Check point Checking method Possible defects
Power supply circuit Q3 emitter voltage —»14.3V Q1~3
D1,2
Constant voltage Q201 emitter voltage —»-9.4V Q201
circuit
Control circuit With arm switch (S1) turned on/off, the voltage S1
(S/S circuit) changes of IC201 terminal (9) are as follows: 1€201
$1 “on" —*7.0V
“off” —~ 0V
Drive circuit Voltage at each terminal of 1C101 (in start mode)
(ST... “on'’)
Terminal | @ @1® @|9|© olel@ @® | @
Voltage |13.7| 9.4/13.6| 3.3 | 3.3 | 3.3 | 3.3 42/64/51
Terminal] @ | @ | ® | @ | @ a D2 ®@
Voltage hashisoiie shoe 06/06] 0 [06/06] 0 | 80
Slol®
~
a
Note: Besides the above-mentioned defects, burnt-out drive coil is also possible. But if it ison one phase, the motor
rotates although the driving torque is halved. Also, it is possible that both Hall elements are defective.
2. Abnormal rotation
| Check point Checking method Possible defects
FG amplifier circuit Solder lead wire to terminal @3 of 1C201; remove Q203
it from the bottom plate and measure the waveform 1C201
in
the
state
of
rotation.
(See
Fig.
17)
FG
coil
pattern
breakage
20ms.
2.8V
a eT, A Vv
Voltage of 1C201 terminal (7) 5.1V
2 Control circuit
(Reference voltage circuit)
Lead wire
TS
Fig. 17
~~) Mie kc} 0 Fc |
3. Unstable rotation (Uneven rotation, repeat of normal and reverse rotations)
Control circuit Measure the waves at 1C201 terminals @) and @).
(Crystal oscillator) 2us.
Possible defects
2.6V
O6V 4 oy
Control circuit
(Brake, timer circuit)
(Stn 28 “on"’)
@) ——>5.9V
@) —4.2V
Control circuit
(Control output
circuit)
Instead of FG signal, apply FG signal by CR
oscillator, (Refer to “How to check the control
circuit.)
Measure the waves at 1C201 terminals @, @, ®.
Note:
Besides
the
above,
it
is
possible
that
Hall
elements
are
defective.
In
this
case,
the
symptom
may
be
that
the
turntable
reversely
rotates
because
the
turntable
position
cannot
be
detected.
4. Others
Check
point
Checking
method
Possible
defects
Strobe LED does not Q202 collector output waveform.
light
up.
10ms.
13V
33/45
r.p.m.
i
Voltage
at
1C201
terminals
©
and
@).
changeover
is
impossible.
®How to check the control circuit
Instruments used Setting
1. CR oscillator 1. Remove the turntable and panel cover.
2. Oscilloscope (Two channel type) (Refer to “Disassembly instructions”)
3. 50V 1uF electrolytic condenser 2. Remove the connector (CN2) from the arm switch.
3. Unsolder the positive @ side of C203.
[22]

Technics SL-Q303 Specifications

General

Brand	Technics
Model	SL-Q303
Category	Turntable
Language	English