So there’s this Asko thing which came with the house, it’s nearly 25 years old I guess. Gave up the ghost the other day, just stuck partway into the cycle, with the timer motor not running.
The only electronic parts in it are a couple of resistors for the neon lights on the front, and a big cap on the circulation pump; it’s all just mains logic. The brain is seven little wheels, controlling seven normally open microswitches, with a tooth or a slot in the wheel connecting one of either pole in the switch. So there’s twenty spade terminals hanging out of this timer unit (one switch only has one pole). Basically the same as a washing machine.
I’ve had the front off it before, with it in situ, to replace the plastic part of the door structure (along with some missing bearings for the tray slider) since it was busted when we got the house, so I had an idea what was in there - this included a circuit diagram! On the back, a chart showing the timing of all the switches! Neoliberalism hadn’t reached Sweden by 2000 (the year of last revision on the diagram).
How hard can it be, right?
I figured it would be worth the trouble to take it out to the front of the garage, where I could hook it up to the tap just outside to test it, and I put it up on a stool to try to make working on it a bit easier…
So I’m taking the door cover off, and it’s an awkward bugger, and it slips out of my grip and cuts my thumb a bit. It also managed to catch and pull one of the wires off the timer unit. There are a few empty terminals… Bastard! I put the wire back on where I thought it came from, and made a note to check it.
Looking around for faults, I saw a wire had somehow lost a spot of its insulation and had made some brown spots nearby… Glad I found that. Not likely to be the problem though. One of the thermostats (there are five, in three separate components, normally closed until the specified temp) seemed to be open circuit, so I got a tab open on eBay for some replacements, but it turned out to be just a low temp spec that took ages to cool down after I pointed the hot air gun at it to test the other thermostat in the package…
Further investigation revealed a dodgy switch in the timer unit. Off with a circlip, out with a pin which doubled as a pivot for some of the fingers in the switch, catch a little finger and spring which were keen to be lost, and there it was. It even just popped apart - there were four layers with the metal of the spade terminals continuing inside, held in place by a push fit in the plastic, nice. So I tediously cleaned the half dozen contacts in each switch, polishing them on the edge of my MDF benchtop, and gave the little spring inside each switch a bit of a stretch for some extra push.
Now all the switches tested nice and consistently, and with the switch unit in the timer, seemed to be actuated properly by the wheels, so I tested for shorts with that one wire hopefully in the right spot. No shorts, so I crossed my fingers and fired it up… Damn. Still no timer motor. I’d have to try and actually understand how this thing works.
So I have a look at the circuit diagram, and I just can’t seem to get my head around it; there’s a whole bunch of components that seem to be only present on fancier models, which makes it really hard to identify which components in the diagram actually correspond with reality… There also appears to be some inconsistency or unlabelled components in the diagram… I just feel like an idiot staring at it.
I give up on the circuit diagram for now, and decide to draw my own. I list all the components and draw lines between them, and end up with a page of tangled spaghetti. I redraw that like four times, successively untangling the layout until I can start to make sense of it, before realising I mixed up active and neutral, and after redoing it another time it makes sense to use ground symbols instead of continuous wires. Now I can finally have a crack at understanding my relatively simple final diagram.
And it’s looking like I definitely put that one wire (I can’t be certain which one now) in the wrong spot. Somehow it’s not obvious how to put it back though. I pull apart the timer again and consult the timer schedule, checking it against the teeth and slots on the wheels to make sure the contacts are properly labelled. This exercise hasn’t really told me much, but it has improved my confidence in the bit of paper.
After two days of banging my head against it, I decide to take another look at the circuit diagram, and I can recognise more of the components. I hit on an angle which makes me optimistic - copy the circuit diagram, but only the bits which agree with my own diagram.
Finally, I discover the discrepancy. The circuit makes sense now, and it works. I skirted with disaster when it nearly fell off the stool a couple of times as I put it back together from a state of near total disassembly…
Hoping it keeps going another 25 years, I go to the trouble of making up some bits in the back of its cavity to jam it in place instead it of always shifting around a bit.
May I never have to think about it again.
