Repair: Mezzo ESM-008 Sewing Machine Power Jack Assembly

Sometimes, the best thing in life is not knowing what might happen next. After I repaired a washing machine using some rather funny trickery, this week, it was the sewing machine that needed attention. The particular sewing machine was a Mezzo branded ESM-008, an Aldi special.

Judging from the label, it would have been on sale in May 2006, making it almost 12 years old. But what is the failure?

Diagnosis

The patient looked okay from the front at first glance, but the problem very quickly revealed itself. Like a patient with a dislocated arm …

… this one had a dislocated socket. Namely, the panel which is involved in the power/pedal input and power switch had somehow popped out of the case entirely. A fracture in the plastic can be seen, which isn’t a great sign.

But it gets worse. With this failure, the rear portion containing exposed live contacts can be touched. I’m sure that this machine might have continued to be used if it were not for the fact that the live wire for either the motor or something else had broken out from a terminal, leaving the ring lug behind.

Repair

I suppose the good news is that the rest of the machine was mechanically sound, so there was no need for me to be concerned. First step is to get into it and get a closer look at how the assembly was supposed to be put together.

To do that, one screw can be undone from the underside to release the side panel entirely.

Inside, we see that the arrangement is like a junction box or even a hobby case. There would have been two screws securing the front portion to the rear plate, and the other two screws (visible) to secure the rear plate to the frame of the unit. It seems that the plastic they used might have been too brittle, the screws may have been overtightened causing plastic cracking or the plug may have been too forcefully pulled/pushed to cause this type of failure.

However, this does mean that there are probably loose plastic parts and screws inside the machine, so I decided to first dismount the plastic plate and the screws and then give the machine a good shakedown. While some loose plastic was dislodged, the screws I expected to find were nowhere in sight. Maybe they got lodged somewhere inside or have been long lost.

Putting the two halves together, we can see that the original eyelet for a screw/bolt has snapped, thus a different solution is required. I decided to use superglue (cyanoacrylate) as it was to hand and fairly strong, but I decided that this shouldn’t just be the only method of securing the front half.

To attend to the wire, I grabbed a section of heatshrink and used a pair of needle-nosed pliers to undo the brass nut and separate the remaining lug. I cleared off the old heatshrink off the lug and cut the new piece to “just” fit while not obstructing the joint.

As the lug was once crimped, and I have no faith in a “loose” brass crimp onto copper, I decided to solder the joint for both mechanical and electrical reasons. The heatshrink was a little short so that I could solder the lug, but in doing so, it had already shrunk over the wire due to conducted heat.

I decided to add a second layer of larger heatshrink that could go over the lug just to be safe. However, I should have probably reduced the overhang slightly to ensure even pressure all-around the brass lug. I don’t think it’s critical due to the magnitude of the current involved and the tension on the nut.

There it is, reassembled into the terminal block.

After running a bead of superglue all around the flat surfaces and pushing together for a good hold, I decided to wrap electrical tape around the two halves in the area that would not interfere with its function. By doing this, if the case halves did come apart, the tension in the tape should stop the whole thing “flopping” out immediately, giving some time for a proper reaction. The tape was a little wide, so I had to use a knife to clear out the lower power plug port.

Once reinstalled into the machine, it fits just fine with the cables tucked neatly underneath.

The final step was to reinstall the side panel and test. The machine worked just fine, as I sewed a piece of paper together, so I would call it a success.

Conclusion

This wasn’t a very complicated repair, but it is a little shocking as to how the design could easily result in live parts become exposed (e.g. tripping on the power input lead a few times might do it). Once damaged, the plastic ears on the jack panel fractured, making a perfect repair impossible. Glue will probably suffice to give the machine a little more life, but whether it is sufficient in the long run given the stresses is something that I’m not certain of. In some sense, this issue might have been reduced if the side panel cut out was smaller than the jack panel or the jacks integrated into the side panel, thus providing some more substantial mechanical support.

But anything saved from the landfill and any purchase deferred is a win in my books.