Repair: Hitachi CL-8320B Rechargeable Hair Clipper

From the same friend that bought around the broken soy-milk maker, I have a new repair challenge on my hands – a Hitachi CL-8320B Rechargeable Hair Clipper.

The Item

The unit was bought to me with its original box, which in itself proved rather interesting. I like the blue eye shields – how cool. The clipper unit is shown on the front, with the “crab” logo which is quite adorably Japanese.

The model is CL-8320 and is branded Sukibari. It claims to be charged in 8-hours.

It has a tiltable head and some sample hairstyles are shown on the side. I find that a bit funny as well – it’s not particularly stunning or enticing, but also, results are hardly guaranteed. If you gave me the hair clippers, I’m sure it wouldn’t look anything like the above!

Diagnosis & Repair

The complaint is a common one with many rechargeable battery operated devices – the unit had been charged but the unit is weak and sluggish and the charge doesn’t seem to last very long. Already, with that description, there was no doubt that the battery was most likely at fault.

Because I thought it to be a simple repair, I had decided to take everything apart to try and replace the battery without documenting anything …

… then suddenly, I ended up with a plethora of parts and … now I thought it might be interesting to take some photos because of the rather simple and ingenious Japanese design.

To replace the battery, it’s not necessary to disassemble the clippers this much – in fact, you could just undo the one screw in the green charger pin cap, pivot out the green end-piece and then lift the cover, undoing two latches near the hinge by applying some pressure to the gap. That would have been sufficient, and would have saved a significant amount of frustration when it came to reassembly.

But since I wasn’t aware how the hinge mechanism was made, I went further by removing the caps from the hinge pivot, undoing a second screw, removing the front clipper mechanism, undoing two screws there and basically stripping the whole unit down. There are a few small pieces as well that could get lost – so I’d advise doing this with care.

The main advantage of taking everything apart is that this unit had hair absolutely everywhere inside. It seems that the slide switch and pivot mechanisms have gaps large enough to allow admission of hair, which then gums up inside mixed with the lubricant.

Anyhow, the way the clipper operates is quite simple – battery is trickle charged via resistor, a switch connects the battery to something similar in size to a hobby motor, the shaft is attached to a brass piece which is “off centre”, riding inside a slot inside the clipper mechanism which converts the rotational motion to a linear one. This then drives a plastic tongue which slots into the rear of the metal blade – et voila, you have a battery-operated hair clipper! There are a few subtleties, such as the tilting head and foil shield mechanism which relies on a lever arm riding inside a channel inside the switch, but that’s really just icing on the cake (and an annoying reassembly issue).

The unit is originally powered by a pair of AA Ni-CD batteries with solder tags. To replace the battery will require a soldering iron to desolder the wires from the tags. The blue wire is the negative, whereas the two red wires represent one from the charging PCB and the other straight to the motor.

As I didn’t have any “tagged” 2xAA series packs to replace it with, I decided to grab a pair of spare old Sanyo Eneloop Party pack batteries and tape them together with electrical tape. I filed the terminals down to ensure there was clean metal available and then I soldered directly to the batteries.

This is not recommended as you can damage the cells or cause an explosion in the worst case. Only do this if you are experienced or willing to take the risk! The first joint made was the “shorting” bar at the far end to put the cells in series.

Then, the joints to the wires of the clippers were done.

As the electrical tape is rather thick, the new battery pack is a tight fit and does cause the body to bulge. A separating divider in the top lid which nestles between the cells was cut as the wrapped electrical tape does not accommodate this.

While reassembling, care must be made to ensure the metal “feeler” that controls the position of the foil runs down to the plastic channel inside the green slide switch.

Moving the slide switch up and down should advance/retract the cutting foil accordingly. If not, you will have to keep adjusting the position until it snaps into place, along with the electrical switch which is located on a PCB which stands vertically in a channel.

Don’t forget the small plastic spring-loaded ball bearing parts that go into the edge to help provide the “detented” tilted positions and retains the cover.

Once reassembled, there is a visible bulge, but at least the unit works well – sounds a lot healthier and lasts about three times as long due to the improved Ni-MH battery. Charging will take longer accordingly, but as they are low-self-discharge type, it shouldn’t matter if it doesn’t get a charge for a while. Overcharge may be a possibility but unlikely, as 8h charge rate for 600mAh Ni-CD cells would be about 112.5mAh which is about 0.06C for the 2000mAh cells, which should be low enough not to cause too much damage as most can handle around 0.025C to 0.1C.

A quick check of the pulled pack with the B&K Precision BA6010 shows that the internal resistance is good, but the cell voltage is poor even after charging. I suspect this means one of the cells may have gone internally shorted due to dendrite formation, but whatever the case may be, this pack is definitely “end of life” after serving eight years.

Conclusion

Rather unexpectedly, repairing this Japanese-made Hitachi rechargeable hair clipper proved to be a rather educational experience on how simple a hair clipper can be made. Its design was nice and easy to service, once you know how to get in and it’s good to see that its screw-based construction means that it doesn’t have to go into the bin once the battery fails. While I had no spare packs of the type originally required, I managed to create my own through (dangerously) soldering directly to battery terminals …

I wonder how much longer this unit can keep going now that it has a new battery that has a much greater capacity …

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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