Mending a microwave

Johnking · 9 Dec 2020

Three year old Samsung microwave has stopped heating. Controls are working, turntable rotates, fans blow, but no heat.

I have seen many warnings not to attempt mending a microwave due to the high voltage that can be stored in the HV capacitor. However, my understanding is that this capacitor can be safely discharged using something with good insulation such as a pair of pliers with insulated handles.

I also understand how to check various components using a meter:

fuses (mains, HV) - continuity tester
HV capacitor - continuity between terminals, and between terminals and body. Resistance between terminals
HV diode - measure voltage when connected to a 9v DC source, test voltage across terminals using both polarities to check it is only passing current in one direction.
HV transformer - check continuity of windings to each other and to case
Magnetron - check continuity between terminals

Because I am reluctant to throw away a mainly-good appliance, and some of these components are cheap to buy, am I foolish to attempt this? I am not qualified, but I've repaired a lot of low voltage stuff, just never touched lethal HV stuff and don't want to die.

EddieM · 9 Dec 2020

How much is a replacement MW. Short answer is it's probably not worth repairing as grating as that may be.

Johnking · 9 Dec 2020

EddieM said:
How much is a replacement MW. Short answer is it's probably not worth repairing as grating as that may be.

About £100 like for like, whereas some ofthe components are a fraction of that. Obvs wouldn't bother if the magnetron was the culprit, but a capacitor, fuse or diode would be worth replacing.

EddieM · 9 Dec 2020

well as you can imagine it's impossible to tell what's failed. At the least I'm glad you know that microwaves are potentially dangerous to work on. At the £100 Mark, I'd be personally cut my losses an replace. Sorry not much use on the repair front.

big-all · 9 Dec 2020

you also have microwave leakage do you have a detector for piece off mind

Johnking · 9 Dec 2020

big-all said:
you also have microwave leakage do you have a detector for piece off mind

Everything looks as new, what would cause leakage other than a visible break?

big-all · 9 Dec 2020

gaps between chassis and cover' door seals leaking 'door twisted or misaligned
microwave are airbourn once produced as a frequency wave so will find gaps

Johnking · 9 Dec 2020

big-all said:
gaps between chassis and cover' door seals leaking 'door twisted or misaligned
microwave are airbourn once produced as a frequency wave so will find gaps

Thank you. So of all is physically as new, it should be fine?

big-all · 9 Dec 2020

Johnking said:
Thank you. So of all is physically as new, it should be fine?

???
unless its leaking??
look up "microwave leaking"
can cause cataracts and other problems highly highly unlikely but its your choice

Johnking · 9 Dec 2020

big-all said:
???
unless its leaking??
look up "microwave leaking"
can cause cataracts and other problems highly highly unlikely but its your choice

I get that leaks would be serious problem, but is there any reason to think it more likely not then before it stopped heating?

I'm not going to replace the magneton, nor interfere with the door.

mattylad · 9 Dec 2020

AFAIK the magnatron itself can be tested - youtube will help with that.
If it has gone then it's cheaper to just get a new one.

big-all · 9 Dec 2020

Johnking said:
I get that leaks would be serious problem, but is there any reason to think it more likely not then before it stopped heating?

I'm not going to replace the magneton, nor interfere with the door.

most things that have operated over a long time faultlessly will carry on the same faultless way
sometimes with a repair or alteration you can get problems unexpected or because off misalignment off components this is why you test and dont assume everything is fine unless the consequences are minimal and fully safe
leakage on a microwawe whilst unusual can happen so its your choice
in my eyes the risk is a small but with possible health issues not worth taking the risk but its your choice

jj4091 · 10 Dec 2020

Johnking said:
About £100 like for like, whereas some ofthe components are a fraction of that. Obvs wouldn't bother if the magnetron was the culprit, but a capacitor, fuse or diode would be worth replacing.

I presume you have already checked if there is an internal fuse blown. Replacing that is about as far as I would go or recommend anyone untrained to go with a microwave. Even then it may have blown because some other component is faulty & will just blow again. I have only successfully done this once with our last microwave & it did last the rest of the life of the oven ( only replaced it because of rust on the inside of the cabinet & yes we always dried it after use ).

Johnking · 11 Dec 2020

HV fuse was blown. Further testing found continuity between terminal and case of magnetron.

RIP.

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Mending a microwave

EddieM

EddieM

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