Akai AP-M50

5-3. ARM OFFSET VOLTAGE ADJUSTMENT
(Refer to Fig. 5-2)
1) Disconnect the connector PS on syscon PC BOARD.
2) Connect an oscilloscope or a digital voltmeter to
TP3, on syscon PC BOARD.
3) Turn the power “ON” and adjust VR6 so that the
voltage is OV +50mV.
5-4. TRACKING SENSOR SENSITIVITY
ADJUSTMENT (Refer to Fig. 5-2)
1) Place a 30cm record on the platter and put the power
“ON”.
2) Connect an oscilloscope or a digital voltmeter to the
TPS on syscon PC BOARD.
3) Press the “ARM-FF-KEY” (<4), shift the tone arm
and bring the arm down by pressing the “CUE” key.
At this stage, fix the arm with a cello-phanetape
to avoid setting down to its rest position.
4) Adjust VR1 so that the DC voltage is OV +0.1V.
5-5. MUSIC INTERVAL SENSOR SENSITIV-
ITY ADJUSTMENT (Refer to Fig. 5-2)
1) Place the 30cm record on the platter and put the-
power “ON”.
2) Connect an oscilloscope or a digital voltmeter to TP2
on syscon PC BOARD.
3) Press the ARM-FF key (<<), shift the tone arm
to the Lead-out area on the record.
4) Adjust VR4 so that the DC voltage at TP2 is 0.95+
0.05V when the tone arm is on the “UP” position.
5) As in the previous steps, adjust the VR5 so that the
DC voltage at TP1 is 0.95V +0.05V.
6) Bring “DOWN” the tone arm to Lead-out area on the
record. Adjust the VR2 so that the DC voltage at
TP2 is 2.2V +0.1V.
7) As same as in section 6, adjust the VR3 so that the
DC voltage at TP] is 2.2V +0.1V.
NOTE: When the sensitivity adjustments (VR2 to 5)
are difficult due to DC voltages are very low,
cut the pattern by removed solder as shown in
Fig. 5-2.
SERVICE MANUAL AP-M50
5-6. SPEED ADJUSTMENT (Refer to Fig. 5-3)
1) Set the test record (33-1/3rpm at 1000Hz) on the
platter.
2) Turn “ON” the power and set the speed selector to
33rpm.
3) Play back the test record (33-1/3rpm 1000Hz). The
playback output frequency is adjusted to 995Hz+
5Hz on the VR1i of MAIN MOTOR PC BOARD.
4) Set the speed selector to 45rpm. The playback
output frequency is adjusted to 1343Hz +5Hz on the
VR2.
Y A
POWER
\yoror
/
MAIN MOTOR TRANSFORMER
PCB
SYSTEM CONTROL PCB
VR2
(33rpm)
FRONT
Fig. 5-3 Bottom View
5-7, LEAD-IN POSITION ADJUSTMENT
(Refer to Fig. 5-4)
1) Set the 17cm record on the platter.
2) Turn “ON” the power and set the speed selector
to “AUTO”.
3) Press the “START/CUT” button. Confirm the posi-
tion where the stylus descends.
4) In case the lead-in position is incorrect, it can be
adjusted by turning the lead-in position adjuster in
Fig. 5-4.
Clockwise direction: The needle’s landing point is
distant from the spindle.
Counter-clockwise direction: The needle’s landing
point is near the spindle.
TOP
LEAD -IN
POSITION ADJ
Fig. 5-4 Rear View