Science and engineering.

[zotz]

Anti-DHMO campaign gathers pace. Official recognition of the hazard can now only be a matter of time (thanks to king_prawn for that one).

Secondly, does anyone know anything about fixing microwaves?

Mine's just stopped heating stuff (although it works fine in all the ancillary ways) and if possible I'd like to fix it rather than replace it. It's nearly ten years old, but it hasn't had hard use and is (cosmetically at least) in very good nick. I've just opened the case and I'd never have guessed that it was quite old.

Now. The only thing I can find out about what's going on inside with my rudimentary understanding of electronics is that a fuse has gone (according to my multimeter). There are two fuses inside, both just inside on a small pcb that also receives the neutral and live lines from the mains lead and has a small transformer on it too (which shouldn't be confused with the much larger transformer in the bottom of the case). One of them is a standard 13-amp fuse indistinguishable from the ones you find in plugs. The other is smaller and unmarked. Plain white. It's the smaller unmarked one that's blown. What the cause of this was I obviously don't know. Where I could find another similar fuse to replace it with I don't know either.

There's an FAQ here which is quite amusing. Careless troubleshooting of a microwave oven can result in death or worse. Experienced technicians have met their maker as a result of a momentary lapse of judgement while testing an oven with the cover removed. Microwave ovens are without a doubt, the most deadly type of consumer electronic equipment in wide spread use.

Rest assured that I have absolutely no intention of messing with the microwave generator or with any of the shielding around the heating chamber or on the door, and nor am I going to plug it in again with the box open. I've taken the lid off, and that's as disassembled as it gets.

The question, for anyone who understands such things, is Does this sound fixable?. I'm certainly not going to try anything more involved than changing a fuse on a machine like this, but I'd rather not drag it round to be looked at, and possibly pay for the privilege, if it's obviously a goner.

Comments

[reddragdiva]

I think you should take in the message of the FAQ and not fuck with it. Chuck it and get a new one. They're really not all that pricey, and a second-hand one should be entirely safe and usable. Preying on the poor and getting one from a pawn shop is a very cost-effective move.

[zotz]

I should have time to check out second-hand shops tomorrow, actually. I could do with a walk.

[sheepthief.livejournal.com]

rudimentary understanding of electronics and microwave

As an electronics engineer I'd just like to point out that I'd really hate to see Fiona that upset. I'm sorry if that sounds condescending, and I really am all in favour of both recycling and saving money, not to mention curiosity. But some things just aren't worth it.

On a more practical note: a) the fuse has no markings - what would you replace it with? b) what caused it to blow in the first place?

[zotz]

Both good questions. If it was just the fuse (or there was a good chance of this) and I had a source for the thing, then I'd replace the fuse rather than the whole thing. If it's more complex than that, then I'd guess that anyone who could fix it safely would probably charge more than it's worth.

You reckon the latter's more likely, then?

[sheepthief.livejournal.com]

Fuses can fail prematurely, but I learned the hard way that there's usually a reason. Still, it wasn't my several tens of thousands of pounds worth of equipment. Anyway, yeah, by all means get someone qualified to check it out - just please don't try it yourself.

[zotz]

No fear.

Thanks.

[hirez.livejournal.com]

Pitch it. Something's gone bang. It'll only be unreliable even if it is fixed.

Jam a scaffolding pole through its guts, just to be sure.

[zotz]

I think I detect a consensus developing here.

[reddragdiva]

In fact, making sure that no-one else will be tempted to mess with the dangerous object is a very sensible move as well. Trash it before trashing it.

[darkstones.livejournal.com]

I'm in the 'bin it camp'. If the fuse has gone then there's a good chance that something else has as well. Furthermore, you need to really trust anyone you get to fix it for you...

Ten years is quite a long time to have a microwave. We don't use use them for business any more, but when we did we had them checked regularly for leaks, which do occur. (You can buy fairly inexpensive sensor devices if you want to check at home folks - they look a bit like the old flash bulbs you used to get for cameras)

One of the EHO's told me a story about inspecting a chinese restaurant and finding that there was a hole cut in the microwave door - 'it's to get the rice in and out quickly' the chef explained......

[deliberateblank.livejournal.com]

Should've called it the 'ricin' slot.

[darkstones.livejournal.com]

Very good!

[deliberateblank.livejournal.com]

Yeah. Unless you know exactly why a fuse has blown (which in my case has usually been because I'm holding a half-melted screwdriver in my hand) it can take far too long to figure out what else you need to fix as well. ("Never eat any animal if you don't know exactly how it died.") It sounds from the PCB layout like it's something on the internal power supply gone - this is far more likely than the actual microwave generator circuitry. The PSU has far more components so there's far more to go wrong. Still, you'd really need to know your stuff to figure out what. (After 10 years my money's on a reservoir cap, but I'm not putting enough money to bet your life on.)

Sod the safety advice in earlier comments - If I knew what was wrong it would still take several hours to isolate and be sure, and several more to replace, fix and test. If you hire someone else to do it then all of the above come with a hefty markup. If you can do it yourself then that time (and components) still isn't free. Given a new or second-hand microwave only costs a few tens of squids is it worth it?

[incy.livejournal.com]

I am going for a bin it. Firstly the fuse could ahve blown in repsonse to another problem,. Secondly unless you are very sure that you are getting an identically rated fuse, the results could well be inconvinent. It is almost certianly not worth paying anyone to repair item, since a new one is almost certainly cheaper then the repair (and after tne years there is a good chance something else will go).

Baaaa

[karmicnull.livejournal.com]

Just following the herd. Bin it, and if so inclined render it clearly worthless and prevent someone winning a Darwin award. Microwaves, DVD's etc are all so scarily cheap courtesy of Chinese manufacturing that it is just not logistically worth it.

[drpyrojames.livejournal.com]

If it was mine, I'd pull the fuse, take it to a local electronics shop and ask if they have a replacement. If they do, chuck it in, put the cover on and try it. If it works, good. If the fuse blows buy another one. No real loss, except for a quid for a fuse, and walk? Fuses sometimes fail for little good reason, so it'd seem silly to bin it for a bad fuse.

[zotz]

That was my first reaction. My second was to wonder how much I'd pay for that fuse and what the likelihood was that there was a more serious fault. If there's only a small chance (which seems to be /Mel/'s view) that it's only the fuse, then I'd probably just be throwing money away. Maybe it comes down to the price of the fuse, which ought to be very little but could in practice be quite a lot for an old machine.