Technics SL-QX300

Turntable does
not rotate
AC 24V between CN1 terminals T1
@ and @). AC cord
YES
DC voltage of regulator IC (C1). $1, D1
@® 29v @ov © 15v C4, IC1
YES
Power supply input terminal
1. DC voltage at terminal (1) of
drive IC (1C101) 15V
2. DC voltage at terminal (18) of
control IC (1C201) ——+8.5V
1€101,1C201
R204, R208
YES
Start/stop and brake circuit
1. DC voltage of transistor (Q401)
ON QFF
\ boas
$302, D401
0401, C401
R401 ~
R403
D402,RL401
$402, 1C201
1C101
Base
OV
|
|
12V 1
Collector 3V
OV
2. DC voltage at terminal (0) of
control IC (I1C201) ——> 0V
3. DC voltage at terminal (2 of
control IC (1C201) + 0.6V
YES
Drive coil and Hall element
1. Conduction check of drive coils.
2. DC voltage of Hall elements.
© | ®@|® |@
Voltage | 3.9V | 7.8Vv | 3.9V | ov
YES
Drive coil
H101, H102
1C101
Drive circuit (Stop)
1. DC voltage at each terminal of
drive IC (1C101)
1c101
——~ | @ | @®@ [@~@
Voltage | OV |15V OV
| Voltage | ov | ov
YES
Drive circuit (Rotation)
1. DC voltage at each terminal of
drive IC (1C101)
2. Waveform between terminal @)
and 6) (© and@) of drive
Ic (1C101).
1C101
NO
3V
33rpm, 303ms (3.3Hz)
Unsatable
rotation
Speed cannot
be changed
Strobe dones
light up
FG amplifier circuit
1. Conduction check of FG coil.
Z. Waveform of terminal (5) of
control IC (1C1201).
33rpm
0.4V : 20ms
45rpm
: 14ms
YES
Quartz oscillator circuit
1. Waveform of terminals (3) and
@ of contro! IC (1C201). 3.5V
awry
rs O.1V 1C201
hse
a
nie
C204~
¢205
Terminal
(8)
Terminal
@)
NO
2. Waveform of terminal () of
control IC (1C201).
VR302 center
| | | | 5V or $301 ON.
Speed control circuit
1 Waveform of terminal (4) ot
control IC (1C201).
1C201
* Stable * Slow * Fast 1C101
Phase control circuit
1. Waveform of terminal 43) of
control IC (1C201).
*In-phase * Phase lag * Phase lead 1€201
1C101
Speed selector circuit
1. Check voltage of terminals
and @) of 1C201.
Terminal (9) is initially at 0.2V,
and only the terminal is kept at
0.2V when S201 or $202 is
pushed.
1C201
$201, S202
D201, D202
R211
YES
Strobe drive circuit
1. Waveform of strobe drive
transistor (Q201).
0.7V
/ \ | \ | | 12V
1€201
Q201
D203,D204
R206, R210
C209
Base Collector
33rpm 10ms. 45rpm_ 7ms.
Pitch control
is detective
Pitch control circuit
1. DC voltage at each terminal of
1C301,
Om KONRON ON
| Voltage | 1.8V| ov | 4.4v] ov]
YES
Input frequency
1. Waveform of terminal (1) of 1C301.
ae a4 1.6V 1.9us.
YES
C.R oscillator circuit
1, Waveform of terminal (3) of 1C301.
hiv VR302 : center | yyy |VR302 C301
137Us.
2.3V
YES
VCO circuit
1. Waveform terminals (7) and (8) of
1C301. 0.5V
® ®) 4
6.5V 1.7V
VR302: center 1.9Us.
YES
Output frequency
1. Waveform of terminal (4) of 1C301. 1C301
VR302: center, 1.9Us R308
4V VR302:—6.5%, 2.04Us
VR302:+ 6.5%, 1.79Us
YES
Pitch control reset circuit
1. DC voltage at terminals 6), ©
and (8) of 1C302.
$301,ON...0V S301, OFF.. .4V
2. DC voltage at terminals (2) and @)
of 1C302.
$301, ON...5V S301, OFF.. .OV
3. DC voltage and waveform of
terminals (8) and (13) of 1C302.
$301,,0FF 55. 5V
$301, ON
5V
1.9Us
4. DC voltage and waveform of
terminals (0) and (2) of 1C302.
$301,ON....5V
$301, OFF 5V
1.9Us
5. Waveform of terminal (11) of 1C301.
Llu
VR302 : center, 1.9Us
VR302 : —6.5%, 2.04Us
VR302 : + 6.5%, 1.79Us