SL-C80
Sony 1984
Betamax SL-C80



beta vcr logo
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.


Loading gear location

Loading gear and shaft repair

The loading shaft for the Sony has no official replacement but most times it can be repaired, unless the gear is in two pieces or a tooth has broken off. There are two approaches to solve this, either repair the broken gear, or purchase a similar gear and adapt it to fit.
  • Replacement part approach
  • White plastic gears (for RC toy cars) are available quite cheaply on eBay that have 10 teeth, a 2.5mm hole and 5.7mm in diameter and 4.7mm in length.

    In practice the diameter is sufficient and the reduced length does not really matter, just use super glue (or other suitable glue) to glue them to the shaft and protrude the shaft 1mm or so past the end. See: RC-Toy-Car gears

    If you don't need 50 then look for a smaller quantity but the price does not seem to change much.

  • Repair of the existing gear
  • Here is how to repair the shaft when it is out of the machine:
    • Remove the black plastic gear from the shaft and then clean the shaft of all plastic residue.
    • Take the gear and pass a hobby knife (or similar narrow blade) down through the gear crack to remove any plastic residue to allow it to close to its correct gap width.
    • Place the gear in a soft jaw vice such that you can apply pressure to close up the gear crack.
    • Now use a drill with the same diameter as the outside diameter of metal drive shafts knurled shaft end to clean out the rough plastic residue from the shaft hole.
    • Take the gear out of the vice. Take the shaft and put super-glue on it and press the shaft back into the gear.
    • Put the assembly back into the vice again (with the shaft facing down flat, gear top facing up) closing up the gap again but leaving about 3mm of the gear exposed above the top of the vice. (note the gap is facing across the vice gap).
    • Drill a hole the diameter of paper-clip metal through the top of the gear and shaft but just below the surface of the top disc.
    • Insert the wire from an unfolded paper clip and turn both ends hard up, then trim off the excess metal. This will lock the plastic gear to the shaft and should keep tension across the gear and not encourage the gap to open up again.
    • Remove any excess super glue from the cracked tooth gap. The repaired gear may make a slight noise in operation but that is only an issue when loading and unloading. It puts the machine back into normal operation versus a scrap heap or spares. The pin clears the drive gear by a good margin and prevents the plastic spinning on the shaft again.

      Thanks go to Noel Higgins for this fix

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

Please click on the button if you are able to contribute a solution to this list or would like to add to, or update PALsite's information on this model.

If you have a question about this model, please raise it on the chatpage.

FaultSolution