Sony 1986
Betamax SL-HF77

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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.
Voltage selector
Voltage Selector

SL-HF77K Voltage Selection

The Karaoke version has a voltage selector at the rear under the power cable allowing the use of AC 110/127/220 and 240 Volt supplies.
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.

Quick fault guide

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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...