SL-HF77
1986
Betamax SL-HF77

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Technical

slhf150 and slhf77 rear view
Rear views

SL-HF150 (top)
SL-HF77 (bottom)

Fault and repair guide

Tape load and wrap mechanism gear breaks

The plastic gear begins to slip on the metal drive shaft because the plastic hardens then cracks under strain. This can be repaired by cleaning out the loose plastic from the gear hole then super gluing and clamping the gap closed on the shaft. The gear can be strengthened by pinning it to the shaft by drilling a 1mm hole through the 'flat' end of the gear and the metal drive shaft and using a section of paper clip metal (1mm diameter) to pin the shaft bending the ends up sharply each side of the gear and clipping them off level with the end of the gear. It might be noisy after the repair because of a slightly increased gap in one tooth but at least it works and the noise is only there on loading and unloading the tape."

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.
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.

Broken gear (left)


Gear assembly

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. Often one of the teeth is missing.

When this happens the faulty gears must be replaced and the mechanism correctly realigned so that the left and right side "tray arms" are at the same position relative to the front panel. This is done by releasing the plastic tab on the gear away from the motor side and selecting the correct mesh position with the teeth of the drive cog on rod which connects between both sides of the cassette tray.

This problem is also found on the SL-F30, SL-F60 and the SL-HF150.

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:
    1. Remove the black plastic gear from the shaft and then clean the shaft of all plastic residue.
    2. 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.
    3. Place the gear in a soft jaw vice such that you can apply pressure to close up the gear crack.
    4. 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.
    5. Take the gear out of the vice. Take the shaft and put super-glue on it and press the shaft back into the gear.
    6. 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).
    7. 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.
    8. 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.
    9. 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. (by Noel Higgins)


Quick fault guide

Please click on the link if you are able to contribute a solution to this list. Add a new quick fault guide entry.

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

FaultSolution
Lack of control of machine functionsFailure of the power supply IC, replace IC.
Failure of the drum motorNormally due to a faulty hall effect sensor. No picture and stops in play, fast forward and rewind after about 2 seconds. Replace the hall effect sensor. It is sometimes possible to help matters by removing the glue on the sensor. If this is not possible, the whole sensor will need to be replaced. Sensors from old faulty reel and capstan boards on dead Sanyo and Sony machines can be used.
Loading ring (Threading Ring)After a very long time of unused machine the the small metallic shaft on the loading ring ten to weaken in order to rising up...this problem due to a weak micro spring of the jack.
Will give picture later on...
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