Betamax PALsite: SL-C40 : Technical

SL-C40

1983

Technical

An unique feature is the 6-pin AV output connector on the rear of this VCR

Fault and repair guide

Stops in play or record

This is becoming a more common problem these days. The first thing to check is that there is adequate torque on the take up spool. If there isn't much then the cause is usually down to two contributing factors.

The first is the drive pendulum which can cease up and the second more serious factor, is wear on the reel motor bottom bearing. The pendulum is simple to replace but the bearing is moulded into the chassis and replacement necessitates that the entire chassis be replaced. One possible compromise is to fit a small piece of plastic into the bottom bearing to raise the rotor and allow it to move freely. Sony supply a repair kit for this purpose.

The repair is as follows: you remove the rotor. Then drop the shim (or small ball bearing) into the hole where the spindle fits. Next you take a file to the bottom of the spindle and gently grind it down until the stator (electro magnets) and rotor (permanent magnets) gap is correct again. This can be tested by spinning the rotor gently with one finger. The rotor should make 3 or more complete rotations with a gentle push.

There's no need to remove the motor pcb. The bearing is integral to the chassis and nothing is gained by removing the pcb. To remove the rotor you just pull. You need to do so strongly and evenly so that you have no sideways movement.

The diagram above shows the pendulum assembly

Stops in play, record and reverse/foreword wind

Do not confuse this with the above symptoms. The problem in this case is due to lack of 4.43MHz colour sub-carrier reference in the servo circuit. This in turn is normally caused by failure of silicon fuse PS1 on the YC-25 board.

Patterning on picture

If you experience a patterning on the picture irrespective of whether you are viewing a tape or not then the most likely cause is that capacitor C319 in the power supply has dried up.

No head drum rotation

You may find that the head drum fails to rotate. This is due to a problem with the Hall effect device on the head drum motor which is secured by a blob of glue which tends to become conductive especially if it absorbs moisture. The best remedy is to remove the glue from the device. To do this first remove the rotor from the bottom of the drum by undoing the lock-nut. Sometimes, however, it is enough to wait for the damp to dry out.

Deck goes into rewind

This can be caused by failure of the tape end sensor. You can check this by unplugging the sensor at its socket on the PCB.

Failure to load a tape

The cassette carriage can fail to operate. This is caused by breakage of the plastic gears in the side of the mechanism. When this happens they have to be replaced.

Quick fault guide

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Fault Solution

Lacing and unlacing incorrect. Suspect failure of the arm block assembly.

No sound during playback. Check relay RY701 on panel AM4.

No take up or chewing tapes. Check the condition and positioning of the pinch roller.

Intermittant squiggly patterning. Pattern is very similar to that caused by C319, but NOT applying to E-E loopthrough. Check Delay Line DL001 on video PCB.

Schema elettrico SL C40 ES Gradirei sapere dove è possibile rinvenire lo schema elettrico del videoregistratore Betamax SONY SL C40 ES
Grazie.
Luigi Lastella
e-mail: lastsoft@libero.it

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