Betamax PALsite: SL-HF100 : Technical

Technical

Inside

Drive

Fault and repair guide

Note, the inside image also shows the power supply can in the top left hand corner with the top removed.

No reel rotation.

A common fault with older machines is lack of reel torque. This can result in the machine shutting down in playback or record modes and the tape not being would back into the cassette housing after eject. The best cure for this is to replace the reel chassis. However, because of changes during production you may find that some other bits, such as springs, may need replacing as well. Sony also made available a 'motor mod kit' which consists of a .02mm thick piece of plastic which can be fitted in the worn bearing. Alternatively a small ball bearing can be fitted but this may require the rotor to be filed down to ensure the correct gap between rotor and stator coils.

Audio level controls not operating.

Check that the audio monitor is set to Auto. The VU meters only show the Hi-Fi sound level in this mode.

Failure of VU meters.

The audio level meters can fail in some segments. Failure is not usually due to defective LEDs but faulty drive ICs. Because of the way this unit is constructed it is not possible to repair and the whole unit should be replaced.

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.

No tape transport

The forward torque pot (third board down at the back near the TV O/P can) gets dry/contaminated changing value which causes tape crease and jamming. CRC spray and a mechanical action back and forth when resetting tension can restore the machine to original performance. If you don't have a torque meter then the rule of thumb for adjusting this is to play the tape and back off the torque until tape just slacks slightly and then turn pot on about 15 degrees. Then confirm tape is not too slack after fwd review/preview actions while searching the tape for a particular scene.

Thanks to Noel Higgins for this tip.

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.

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

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

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

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