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General information

 

Job Number

 

0204-48

 

 

 

 

Equipment type

 

Long Play, Cassette recorder and tuner stereo amplifier

 

 

 

Maker + Model #

 

National Panasonic SG-1070L

 

 

 

Made in

 

Japan

 

 

 

 

Comments

 

Very old, but in good state. It seems that this had the first prototypes of STK power amp integrated circuits.

 

 

 

Symptoms observed

 

 

BAD

1

 Cassette and long play sound noisy & low definition

 

 

 

 

2

Long play arm moves rapidly without playing music

 

 

 

 

3

 FF and REW of cassette part sloppy and slow

 

 

 

 

4

 Volume and balance pots noisy on adjusting

 

 

 

GOOD

1

 Powers up, and good sound output

 

 

 

 

2

 Tuner sections works perfect

 

Repair notes

 

Full repair description and observations

 

1

 The arm used to move fast because of the wrong alignment of the needle. It has to be perfectely perpendicular to the longplay. The needle was repalced and fitted in place and the moving arm fault and the noisy sound from the long play were fixed

 

 

2

 The cassette heads were thoroughly cleaner with iso propyl alcohol, and the sound on the cassette unit improved very much

 

 

3

 The rewind and fastforward problem was due to an old weared audio belt. Actually there was 2 belts, one used to drive the play/ff/rew mechanism from the motor, and one to make the counter to operate. Both belts were replaced. This meant to dismount the cassette compartment since the former belt could not be reached.

 

 

4

 The volume noise problems was arranged by the usuall contact spray servicing to the corresponding potentiometers

 

 

5

 Further servicing, such as greasing the motors and cleaning the deck were further performed.

 

 

6

 The unit was mounted back carefully and gave a final cleanup to the outer casing.

 

 

7

On testing the turntable, it was noted that the sound output on the longPlay section was very low, while ok on the Tuner and cassette section.

 

 

8

On applying an external sound output to the connection where the LP sound input is fed, the sound was amplified normally, hence the fault is in the pickup of the sound from the needle.

 

 

9

Since the needle was new, the fault is in the ceramic cartridge, and a replacement could not be found yet. On examining other cartridges, it was noted that probably the fault was due the fact that the cartridge had a missing part – a connection between the needle and the ceramic pickups. When such a part was home made with plastic-rubber material, the sound improved slightly!

 

 

10

 

Attempts to find a replacement cartridge from local shops or the internet failed!

 

 

Repair summary

1)    Wrong needle adjustment

2)    Old needle diamond

3)    Worn and old rubber belts in the cassette unit

4)    Dirty volume/balance potentiometers

5)    Parts missing from the ceramic cartridge pickup.

 

 

 




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