Technics SL-Q303 Service Manual

SL-Q303
Control circuit
@ BLOCK DIAGRAM
Drive Circuit
8
1C201 (AN6680)
X201
O
9 1C101 (AN6635)
8
Output amp.
°°
6
2
a
a
3
(3)
oO
w
Output amp.
Drive coil &
®
fk
Cy)
Strobe illuminator
9on
8
3
>
as]
¢
g
=
&
3 | RL201
|i Start/stop plunger
$1. off
(Arm switch)
Speed indicator
Oo S2 Ee b (Start/stop)
Rectifier
Power
transformer
SL-Q303
m TROUBLE SHOOTING GUIDE
1. No rotation
te Check point Checking method Possible defects
Power supply circuit Q3 emitter voltage —» 14.3V Q1~3
Di, 2
Constant voltage Q201
circuit
Control circuit
(S/S circuit) 1C201
Q201 emitter voltage —»-9.4V
With arm switch (S1) turned on/off, the voltage
changes of 1C201 terminal @ are as follows:
$1 “on” —7.0V
“oft” —_> OV
Voltage at each terminal of 1C101 (in start mode)
(SVs cis “on’”’)
Terminal] © | @ sal HEF ® ® o | @
Drive circuit
Voltage |13.7/ 9.4| 13.6] 3.3/3.3/ 33/33] 0 | 42/64! 5.
T
@ | ® @|@/|@/|®@
0.6/06| 0 [06/06| 0
Terminal | ® | ©
Voltage |14.3/13.7/14.3/13.6
Note: Besides the above-mentioned defects, burnt-out drive coil is also possible. But if it is on 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
20ms
breakage
4 . ; \ VA 0.4V
2.8V
oe ee HG V
Voltage of 1C201 terminal (?) 5.1V
Control circuit
(Reference voltage circuit)
Lead wire
ae
Drive
circuit
P.C.B.
Fig. 17
SL-Q303
3. Unstabl
2 Contro
(Brake,
Note: Besided |
turntaq
eHow to check
Instrument
1. CR oscillator
2. Oscilloscope
3. 50V 1uF eleq
|
Fz |

Technics SL-Q303 Specifications

General

Brand	Technics
Model	SL-Q303
Category	Turntable
Language	English