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Sony 1984
Betamax SL-C80



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711B CHASSIS

Technical

Sony Betamax SLC80 rear
SL-C80 rear
The SL-C80 shares some similarity to the SL-C30 both having the same 711B chassis. It also shares the same heads as the SL-C9.
Power supply layout
Power supply

Power supply layout

This machine has a somewhat unusual power supply and board layout. The unit itself is also quite deep.

Fault and repair guide

Pendulum
Pendulum

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 shows the pendulum assembly.

Stops in play, record and reverse/forward 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.
hall effect sensors with glue
Hall effect sensor attached with glue

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. Full details on how to fix this can be found on the head motor page.
pinch roller
Pinch roller

Pinch Roller

Over time, the pinch roller surface will become polished which can reduce its ability to pull the tape through correctly. It is recommended to clean or replace this.

See also: Parts - Pinch Roller for information on how to fix this.


Quick fault guide

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