Microwave oven

Mar 22, 2019 67 Replies

Hi all,



I have had the same Daewoo microwave oven since I bought it new 7 years ago and it's always performed *perfectly* up until today. This morning I stuck some bread in it to defrost and it came out still frozen. No trace of any heat at all. The platter rotates, the light comes on, the timer counts down, the fan runs; all is working fine except for the total absence of heat. I'm given to understand that microwave ovens typically have a working life of only around 2 years nowadays, so I'd really like to fix this one up rather than replace it with something inevitably inferior. Any suggestions as to what to check for? I have the gear to measure up to



50kV if necessary, and I'd guess the magnetron HT is considerably less than that figure. So... where to start looking first?

This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

Likely candidates are the HV diode & HV fuse. Of course it can be other things. And of course they're in the killer section.

NT

The easy place to start is with the door switches. Microwaves usually have several as a fail safe.

With the microwave running, watch the interior light carefully and listen f or any change in sound as you slowly rock the door. If the light dims and you hear a buzz begin, you've got a cranky safety interlock switch. There could be a broken activator tang as well and it might be visible right on t he door.

Inside, the relays are known to develop cracks in the solder at the pc boar d, so leaning on the relay and edge connectors could restart the cooking.

Familiar territory then. I've spent god knows how many years prodding around inside the HT cages of CROs and whatnot.

-- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

That's good.

Re interlocks, they're designed to short out via a power resistor if any on e fails to operate correctly. So usually interlock failure results in an oc shorting resistor - which is a hazardous state in which to run a nuke. So it's always worth checking continuity of the big resistor when you have the cover off. IME interlocks are low on the list of likely suspects.

NT

Replacing the lamp has me defeated. I buy a new mwave then.

I don't want a new one, though! The existing one is built to an amazingly high standard and the manufacturer has taken time and trouble to finish it beautifully as well. I'll struggle to find anything around today that comes close to that quality.

This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

Most of the tests can be done with the power off (continuity checks)...to summarize: Ck door switches Ck power resistor Ck HV diode Ck magnetron Ck HV transformer

I won't repeat/elaborate on these but here is some detailed diagnostic techniques.

formatting link

Ebay is a source of parts, especially magnetrons at reasonable prices. You will see the name Galant as a mfg. The produce something like 70% of the worlds magnetrons and they sell to everybody (panasonic, toshiba, daewoo, etc, etc. Most of the others are low quality knockoffs...YMMV

You should search online for a schematic for your unit...all will become clear with that in hand. Fairly simple. J

If it's mechanical control, the circuit is much the same for them all. And the cct is usually printed inside the outer cover. Why they're the one appliance to have that I don't know.

NT

Sometimes the relays go intermittent. Try tapping them with an insulated probe if it isn't door switches, themal cut-off sensor, filament connections, HV diode or capacitor.

** Massive false assumption.

** There is no comparison - microwave ovens are highly lethal to repairers, hundreds of times more so than scopes.

Never play down the risk, that would be a criminal thing to do.

.... Phil

but the techniques for dealing with EHT are the same. He's an electrical guy with experience with EHT, not a random newb.

did anyone? No.

tabb...is a dangerous MORON

** That is another dangerous false assumption.
** More likely to make him careless with a microwave oven.
** Yawnnnn....

** Well, you just did and so did he.

But having wanked yourselves bind you cannot read your own posts.

** Complete f*****ts like you and CD need a giant kick up the arse.

I could not give a S*IT about either of you being electrocuted - but there are others who read these pages and they are not so deserving.

.... Phil

I'm pretty sure how I approach it is safe, but enjoy your trip.

Phil would probably like to see me and several other posters here dead if the truth be known. There is so much hatred in that man. Fortunately, since I perma-plonked him some time ago I rarely have to see his so- called "contributions" any more. I could accept Phil's attitude problem if he gave 100% accurate advice, I'd happily ignore all the bile as a personality quirk, but he's frequently wrong and when that's pointed out to him he invariably attacks whoever exposed it in the most visceral way. I struggle to see how personal attacks are going to improve his credibility, but if that's what he believes there's nothing you or I or anyone else can do about it.

This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

Many thanks for that info. This is also worth a look:

formatting link

This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

** Just all the trolls - like you.

** Yep - I hate trolls.

They ruin newsgroups for everyone.

** What a gutless waste of space you are.
** No such thing is possible or required of anyone here.

You are completely insane.

** FFS prove it - not once have you ever done that.

You lying pile of s*it.

..... Phil

*CAN* kill. *Not* WILL. Depends on *several* factors so your "no doubt about it" is incorrect. There is one large fat potentially-lethal capacitor in there that needs to be discharged as the first job to do after the removal of the outer casing. It doesn't appear to have a bleed resistor for some reason (not with this particular oven anyway.)
This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

I don't doubt it.

Yup

It would be sensible to say microwaves can electrocute people, not so sensi ble to insist everyone, despite not knowing what skills they do or don't ha ve, does not have the necessary skills to work with them. It's not difficul t, just need to know the issues/gotchas. There's EHT, soakage, leakage, and the principles of the interlock system. Otherwise it's just more electrica l equipment, with its design quirks like the transformer.

NT

See, you politely disagree with him and all you get in response is a load of foul-mouthed abuse. As if that's really going to win people over! :-D

-- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required