Job Number

0010-09

Equipment type

HiFi  - Stereo cassette deck recorder

Maker + Model #

MARANTZ – SD451

Made in

Germany

BAD

1

Playback stops after few seconds.

GOOD

1

Powers up

2

Fast Forward and rewind OK

Repair summary

Rejuvenated the motor of the tape rotator

Full repair description and observations

1

The cassette section could not be dismounted since there was a very tight screw which prevented the power supply from being removed. The power supply blocked the way for the cassette to come out.

2

There were 2 separate motors, one, which was large, metal, coated and was responsible for driving the pinch roller, while there was a smaller one, partially of plastic which drive the tape rotator. It seamed that the problem was from the latter motor / section

3

When free, this motor rotated perfectly, but when loaded with a cassette, it had no power to drive it. Contact spray on the cassette mechanism did not improve the situation at all.

4

The motor was connected with an external power supply of about 7.5V, and this rotated at

very high speed. The actual operating voltage was about 2.6V. Fortunately, the excess voltage did not made any damage, neither to the components on board, nor to the motor itself.

5

This operation seemed to be very useful because on loading a cassette, the playback began to work perfectly! The motor was rejuvenated, and any grease/dirt was removed away.

6

The deck was assembled back to place and several cassettes were tested. Once it coiled the tape after being left on playback (with repeat function on) for 4 hours or so

7

Since I was not very happy with what happened and since I found a cheap replacement motor at Mapp, I decided to replace the motor because it would be a bette repair job. The problem was that the motor was a bit bigger and could not fit easily as the original motor, but by various ways and means it was fitted in palce.

Precautions, fouls and advises

1

It would have been safer if the external voltage supply was given to the motor being disconnected from the circuit. The higher voltage could have caused damage to the circuit.

2

While testing the deck after being fixed, a tape was left for more than 4 hours playing. It got coiled very badly, that it could not get ejected, and eventually had to destroy partially the tape. Some sort of minor damage was caused to the deck as it began to make some whining mechanical noise on playback. On testing more tapes, it did not caused the problem again.

3

Study well the problem before dismounting, so that you can go to the exact part to be serviced. I took about 1 hour of studying to notice that the tape motor was the suspect part.

1

Power supply voltage (from ribbon output):

Pin 1

GND

Pin 3

5.7V

Pin 5

11.8V

Pin 7

12.3V

Pin 2

-5.1V

Pin 4

6.1V

Pin 6

13.4V

2

Motor operating voltages:

Pinch roller

12V

Rotator

2.3V

3

ICs present in circuit:  (some are Panasonic)

BA 335 (9 pins)

TA 7405p (8 pins)

LM 6402h (42 pins)

HD 3870 1A08

TD 62504 (16 pins)

TEA 0665 (28 pins) x 2