What lies beneath this ancient plate that no one has looked inside for nearly a million, well 40, years?
A while ago, the Snail bought a 1970s’ vintage Bernina sewing machine, which is way too scary for me to use but that she drives without a care in the world, not knowing that it is clearly haunted by the ghost of a, well, suffice it to say, a ghost. The other morning, just as the sun was rising*, that ghost manifested itself.
The sewing machine just started sewing. On its own. No one around.
For one such as I, who is terrified of these electric sewing machines (or crazy-electron-using-thread-knotting hell-machines as I call them), it was only after more than the usual number of tots of rum for breakfast that I was told the awful truth: this is a known fault and it really is simple to fix.
Calling the issue a “fault” is unfair. Bernina machines are built to last forever, presumably so that when they inevitably acquire the machine equivalent of a soul at some point, they can take over the Universe. Anyway, brushing away the image of a walking foot being chancellor of the exchequer for a moment, there is a capacitor (I’ll explain in a bit) in the foot pedal controller thingy** which is manufactured such that it has a lifetime of around just 30 to 40 years. Imagine that! Imagine a mobile phone built to last more than a quarter of a century! Nope, me neither (<goes off for a quiet internal monologue-type rant>).
OK, what in blogging hell is a capacitor, I hear you cry (or is that my internal monologue too?). Well, it is a thing that stores electricity for a bit and then discharges it, so it effectively smooths out ripples in the water-like flow of electricity (if electricity flowed like water. Which it doesn’t.). Here, I think it just makes the speed of the motor smoother as you use the pedal. This type of capacitor uses a layer of paper and a layer of metal to produce the desired effect. After 40 years, the paper has broken down (much as I did when I was 40), so the two ends are essentially connected and the whole thing passes electricity all the time, irrespective of where the pedal is and whether there is actually a human operator present. This machine is a whisker away from ticking that box that says “I am not a robot” and getting away with it.
Fixing the capacitor is, in theory easy, provided you have the right replacement capacitor. Now, you can buy ones specifically for such pedals OR you can use a light bulb, obvs.
As I have ranted on about before explained before (here), modern energy efficient light bulbs (the compact fluorescent and LED kinds) have some electronics in to make them work. When the light-making bit stops making light, all the electronic components are destined to be, at best, melted down, at worst, left in landfill. Whether energy efficient bulbs (CFs or LEDs) are better overall for the environment is a whole other rant for another day. For this day, such a circuit board was recovered and a suitable capacitor – right capacitance value, size and voltage rating – was rescued from a melty/landfill future to live its life in the volume***, I mean, speed pedal of a sewing machine. I bet its what that capacitor grew up wanting to do.
After 40+ years of loyal service, this capacitor has gone all gooey on us
473K400? But you don’t look a day over 25…
I assumed that it would take me ages to scavenge a new component, but a bit of an old CF bulb was lying on my workbench, actually on top of the junk, er, useful things that live there. And you know what? That brown sweet-looking thing marked 473K400 was perfect – being, as it is, a 0.047 microfarad 400 volt capacitor and not a piece of gone-off strawberry chewing gum. The original capacitor was also not a piece of gone-off strawberry chewing gum but was, in fact, a 0.05 microfarad 250 volt capacitor. Happy days, if you are a nerdy electronics geek like me.
New capacitor, ready for 30 years’ service
As you can see, the new capacitor is much smaller than the old one and rated at 400 volts rather than 250, which means it should be even better! Whether it will last longer, I wouldn’t like to say. Ask me in 30 years…
Help! There’s a bee using the sewing machine!
* Apart from the implicit plagiarism of song lyrics, the sun did not so much rise as hide behind the rain the whole day.
** Sorry, being technical again.
*** Oops, I play electric guitar and am way more used to volume pedals.
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