It should be noted that The Restart Project refuse to repair these because they think it’s dangerous, I would be curious to understand from those that know, why they think that, if it even is.
Microwave ovens are Dangerous. I have done microwave repair before . The cap you speak of is a bit of a kicker and can kill! lethal amounts of voltage and current combos in side!. YOU ARE DEALING WITH A HIGH VOLTAGE HIGH CURRENT DC POWER SUPPLY SO BE EXTREMELY CAREFUL!
There is actually very little to a microwave other than the control circuits.
its a magnetron, Diode and capacitor. the diode has a very high depletion region and needs a large quantity of voltage to over come this, so can not be measured with a multimeter alone. this can be the culprit as it dissipates a lot of heat when functioning. and with all electronics you look at heat sources first when troubleshooting.
magnetrons usually are quite visual when the break.
I was of course hoping it was a blown fuse or some obvious visible failure…and not go exploring further than that.
On the subject of danger: we talked about microwave ovens a couple of weeks back, and I said that I wouldn’t try to tackle one. it being the modern equivalent of a CRT TV for a high voltage and current home appliance, plus the magnatron always seemed like a death ray to me.
However it was suggested that with careful handling it wasn’t such a risk.
I now think I was probably wrong to do it, and realise why Restart won’t touch them. It’s too easy to make a mistake, for someone to walk past and touch an exposed terminal, to cycle the power several times and forget just once to check the cap is discharged…And Restart is all about the public being able to fix their stuff at home the next time it breaks. And Makerspace is populated by curious people…
So: @joeatkin2 said a while ago “no high tension electrics”. Is this the best course? Whoever takes on the @tech roles for electronics should probably look at and define this.
I would go with ‘experienced supervision required’ when handling mains. I
voiced my concern to Joe when I started when he ruled out main voltage but
do agree we need to look at safety more closely regarding this. and I’m
not saying you guilty on this but stating it for all to hear " if it’s off,
it does not always mean it’s safe" as for a broken microwave I agree with
trying to fix it and commend people who choose to fix something instead of
dumping it and buying a new one, so please don’t let me discourage the
educational and recycling value of this.
Oh and as for microwaves being equivalent to TV’s yes and no a TV tube
runs between 11000v - 26000v but at relative low current but still
dangerous levels. A microwave is around 2kv - 8kv but much higher current
LETHAL levels in fact with no chance for chalking it up to being healthy so
a little shock won’t harm type of banter.
also remember these high voltages like to jump so just because you don’t
touch it does not mean it wont bite.
This is a reminder to all to be safe. but don’t be scared. trying not to
make this sound like I’m talking to my kids, sorry
Well, I’m always minded to fix things, and didn’t go at the microwave lightly. Had a heightened awareness around the fact that it was HT. And never intended to test or go near anything live. Though now I’m wondering if discharging the cap through a resistor held in insulated pliers is okay practice?
So I agree with you. Supervision is needed.
I’m experienced with domestic mains, but this is a different world.
The transformer in an old microwave can be used as the basis of a spot welder. In essence the secondary is unwound and then a couple of turns of heavy gauge wire are wound on instead. This gives a low voltage, high current output.
but don’t be scared. trying not to