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For Europe model

SERVICE MANUAL
MODEL DRR-M31
STEREO CASSETTE DECK

Some illustrations using in this service manual are slightly different from the actual set.

16-11, YUSHIMA 3-CHOME, BUNKYOU-KU, TOKYO 113-0034 JAPAN
Telephone: 03 (3837) 5321

X0166V.02 DE/CDM 0302
DRR-M31 2

SAFETY PRECAUTIONS
The following check should be performed for the continued protection of the customer and service technician.

LEAKAGE CURRENT CHECK
Before returning the unit to the customer, make sure you make either (1) a leakage current check or (2) a line to chassis
resistance check. If the leakage current exceeds 0.5 milliamps, or if the resistance from chassis to either side of the
power cord is less than 460 kohms, the unit is defective.

2
DRR-M31 3

DISASSEMBLY
(Follow the procedure below in reverse order when reassembling)

1. TOP COVER
(1) Remove 2 screws fixing from the both
sides.
(2) Remove 5 screws fixing to the Rear Plate,
then detach the Top Cover in the arrow di-
rection .

2. FRONT PANEL
(1) Disconnect 1 HCU joiner coming from the
front P.W.B.
(2) Remove 4 screws fixing the Front Panel at
the bottom.
(3) Whil releasing 2 hooks, detach the Front
Panel.

3. CASSETTE MECHA. ASS'Y
(1) Remove 4 screws fixing the Cassette
Mecha. Ass'y.
(2) Disconnect 3 connectors, then detach the
Cassette Mecha. Ass'y.

3
DRR-M31 4
4. REAR PLATE
(1) Pull up the Power Cord together with the cord
bush to disengage from the Rear Plate.
(2) Remove 3 screws fixing the 4P pin jack and
AC outlet respectively.
(3) Remove 1 screw , and detach the Rear Plate.

5. MAIN P.W.B.
(1) Remove 1 screw fixing the AMP P.W.B.
(2) Pull up the AMP P.W.B. as shown in the arrow
direction, and disconnect 2 connectors.
Connector
(3) Remove 4 screws fixing the Main P.W.B.
(4) Release 3 pieces of P.W.B. spacers.
(5) Disconnect the connector from the Trans Unit.
(6) Take off the Main P.W.B.

AMP

6. DISPLAY P.W.B.
(1) Pull out the knob (E).
(2) Remove the nut and washer for the rotary
switch.
(3) Remove 9 screws .
(4) Take off the Display P.W.B.

4
DRR-M31 5

ADJUSTMENTS
ADJUSTMENTS
Adjusting and Checking the Mechanism Section

1. Replacement of the pinch roller 4. Adjustment of the recording/playback head
Before replacing the pinch roller, clean the tape contact Azimuth adjustment
surface of the pinch roller and the tape contact surface of Load side A of the A-BEX TCC-153 test tape facing
the capstan shaft. After replacement, run a C-90 tape forward, and adjust.
without a pad and check for the presence of tape curl at (1) Play in the FWD direction and turn the azimuth
the tape guide portion of the head. adjustment nut for the FWD side so that the
Lissajous's figure becomes maximum at (A) and
minimum at (B).
(2) Play in the REV direction and turn the azimuth
2. Checking the pinch roller pressure adjustment nut for the REV side as adjusting the
Set to the playback condition and hook a bar-type spring FWD side method.
scale to the bracket above the center line of the pinch (3) Adjust (1) and (2) again.
roller. Pull the pinch roller away from the capstan shaft, (4) Apply screw lock to the adjustment locations.
then allow the pinch roller to come into contact with the
capstan shaft and check that the reading of the bar-type
spring scale is between 2.45 N~3.92 N (250~400 g) when
the pinch roller starts to rotate or pull force indicates more
than 7.85 mN (80 g).
Replace the pinch roller when the value falls outside of
the specified range.
PB Amp
LINE OUT
L
Capstan shaft
V
Pinch roller R H

A-BEX TCC-153

2.45 3.92N
(250 400g)
REC/PB HEAD

3. Replacement of the recording/playback head
assembly
A B
3-1 Removal of the head assembly
(1) Remove the 2 BRACKET-HEAD fastening screws.
FWD SIDE REV SIDE
(2) Remove one screw fixing P.W.B.
3-2 Mounting the recording/playback head assembly
Perform by following the steps of Section 3-1
Removal of the head assembly in reverse.
5. Checking the winding torque
Load a cassette type torque meter (Sony TW2111A at
the FWD side) and check that the reading of the torque
meter during playback is
294 to 686 mN-cm (30 to 70 g-cm) at the center value.

6

5
DRR-M31 6

6. Checking the back tension torque at the time
of recording and playback 8. Checking the FF and REW time
Load a cassette type torque meter (Sony TW2111A at Load a Type 1 tape (UD-1), and check that the time for
the FWD side, Sony TW2121A at the REV side) and check FF and REW is less than 120 seconds. When outside of
that the reading of the torque meter during playback is the specified range, check Steps 5 and 6.
9.8~58.5 mN-cm (1~6 g-cm) and that there is no
unevenness. 9. Checking the erroneous erasure prevention,
and the metal and chrome switch operations
7. Checking the FF and REW torque Check that detection lever is operating the switch properly
Load a cassette type torque meter (Sony TW2231) and depending upon the presence or absence of a hole.
check that the value indicated by the torque meter for
winding and rewinding is between 686 mN-cm~1.47 N-cm
(70~150 g-cm).

Adjusting and Checking the Electrical Section
Measuring instruments needed for the adjustments 2. Tape speed check and adjustment
(1) Low frequency oscillator (1) Connect the frequency counter to the LINE OUT pin
(2) Variable resistance attenuator and load the test tape (MTT-111).
(3) Electronic voltmeter (2) Playback FWD side of the test tape. At about halfway
(4) Oscilloscope through the tape, where the tape transport is stable,
(5) Frequency counter confirm that the frequency counter will have a
(6) Adjustment screwdriver reading within the range of 3,000 Hz