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Serviceman's Log

Watchmaking is not exactly my forte but I'll take on just about anything these days to try to make a dollar. Sometimes my efforts are successful and sometimes they aren't but it doesn't hurt to at least try.

by the Serviceman

Items Covered This Month

• Watchmaking is not my forte

• Buzzing recording studio

• Of mice & Triacs on a chook farm

• The spider & the Hereaus photo-polymiser machine

• Faulty LG dishwasher

• Soniq E19Z10A 48cm TV

*Dave Thompson, runs PC Anytime in Christchurch, NZ.

I’ve said it before and I’ll say it again; in the current economic climate here in Christchurch, I’m prepared to have a look at anything that needs fixing, as long as the client is prepared to pay for my time. The other day, for example, I turned my hand to wristwatch repair although I have to say right up front that this type of work is not really my bag. However, someone asked if I could fix such things and since I am always a soft touch, I said I’d have a look.

Of course, if it had been a wind-up watch, I wouldn’t have even bothered opening the back. Those types of watches are strictly for the professionals. And with new watches now selling for peanuts, it’s seldom worth repairing run-of-the-mill watches anyway.

In this case, the watch apparently had sentimental value and after agreeing on a reasonable “dollar-cap”, I got stuck into it. The problem with this 8-year-old ladies Casio quartz timepiece was that the hands had stopped moving. Usually, when something like that happens, the battery has gone flat and replacing it fixes the problem. However, when I pressed the illumination button on the side of the watch, the LED backlight told me that there was plenty of juice left in the battery.

Click for larger image

The first thing to really become apparent when I started working on the watch is that when it came to handling the tiny screws and other micro-fittings, I suddenly felt as if I had fingers of butter and fists of ham – and that’s despite being able to handle surface-mount parts on PCBs. I also discovered that a decent head-mounted magnifier is essential for an aging serviceman to be able to even see what is going on. Fortunately, I have a set which I modified to use high-intensity LEDs instead of the old incandescent globes it used to have. Nothing beats good lighting when doing such fine work.

However, while my illuminated magnifier was a great start, my other tools fell short. All the screwdrivers, pliers and tweezers I normally work with were suddenly way too big and totally impractical for watch repair work. Even the smallest flat screwdriver in my set of so-called “jeweller’s screwdrivers” was too fat for this watch’s miniature screws.

However, I also have some ultra-small screwdrivers and tweezers, along with some other micro-tools, stored away from my aircraft engineering days. They’ve been sitting in a drawer, unused since my time in the instrument repair shop.

As it turned out, I didn’t really need them because as soon as the watch’s back was removed, the problem was obvious; a pale green “fuzz” coated the entire insides. This “fuzz” was mould, caused by moisture getting in, and it had wreaked havoc with the sensitive electronics and clockwork mechanisms.

It didn’t take a crime-scene investigator to figure out why this had happened. A sorry-looking, chewed-up O-ring lay among the mould. This thin rubber seal is usually placed in a small notch cut around the outer edge of the housing at the back of the watch. When the back-plate is clipped in place, it slightly compresses the O-ring, sealing the interior from the elements and hopefully preventing moisture getting in.

In this case, the O-ring hadn’t been seated properly and at some stage in the past, had been crushed and partially severed when the back had been pressed on following a recent battery change. As a result, there was virtually no seal at all.

At this point I knew it would be highly unlikely I could repair this watch, though I persevered out of interest. First, I removed three tiny screws that were holding a thin spring-plate to the rest of the movement. This was then eased clear of the movement and I could then actually see light reflecting off the moisture that had gathered underneath it.

The PCB, which occupied about a third of the room inside the case, was semi-circular in shape and contained several surface-mounted resistors and capacitors, along with other unidentifiable components. At one end, a tiny cylindrical crystal nestled into the movement’s plastic moulding while at the other end sat a coil of ultra-fine wire. I assumed that both were part of the oscillator timing circuit.

Undoing two more tiny screws released the circuit board which I then carefully removed using tweezers. Like most modern circuit boards, it had been coated in a clear, hard lacquer but every exposed soldered or metallic area had still been significantly corroded.

When confronted with circuit boards like this, I usually break out my fibreglass PCB cleaning pen. This invaluable piece of workshop kit is like a wide-tipped marker pen but instead of having a solid felt ink dispenser, it has stiff, brush-like bristles made of strands of fibreglass. An adjustment wheel at the top end of the pen winds the bristles in or out of the barrel, to give a gentler or harsher action.

It’s an excellent cleaning medium for stripping the likes of flux or even burnt fibreglass from a circuit board, or the aforementioned lacquer or corrosion. Anyway, I got stuck in but after cleaning the board, it was obvious that the prognosis was terminal. Even if I had the eyes of an eagle and a pin-sized soldering iron, I seriously doubted whether I could repair the tracks.

The only realistic option was replacement. I had a good look on Google, Casio’s web site and the sites of various Chinese manufacturers to see if a spare movement was available. It was but as is always the way with spare parts, a new watch would cost far less than the spares, delivery and labour, no matter how cheap my time goes for these days.

In the end, I put it all back together and returned the watch to its owner, who now has it sitting in a drawer, not wanting to throw it away. I didn’t have the heart to charge because I hadn’t done anything other than confirm what I already suspected before I started the repair.

The moral of this story is that if the guy who replaced the battery a few months before had done his job properly, the watch would still be going. And it would have lasted many years longer, all for the sake of a 5-cent O-ring. Next time you get your watch battery changed, ask the salesperson to check the seal; it’s well worth paying a bit extra to have it replaced.

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