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Microwave Ovens? #135767
02/03/03 12:26 AM
02/03/03 12:26 AM
Trumpy  Offline
OP
Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
I've got a faulty Microwave, in the w/shop,
it will cook food OK, but, after a time, if used to defrost food, for more than 19 minutes on 10% power, it will reset itself, half-way through the programme and just stop.
I have checked all of the obvious faults, but I am at my wits end, with this one.
Can anyone else help me out?.

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Re: Microwave Ovens? #135768
02/03/03 08:06 AM
02/03/03 08:06 AM
D
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
sounds like a software / firmware error.

Replace PCB logic board..

Re: Microwave Ovens? #135769
02/04/03 11:37 PM
02/04/03 11:37 PM
Trumpy  Offline
OP
Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
djk,
You reckon this might be the problem?.
It is quite an old M/wave, not sure if parts are still available, might be better to junk the thing.
People that own it,want it fixed, I may have news for them. [Linked Image]
Does anyone have a basic Circuit Diagram for the Power circuitry of a M/wave Oven.
Please Help, if you can.

[This message has been edited by Trumpy (edited 02-04-2003).]

Re: Microwave Ovens? #135770
02/05/03 07:21 AM
02/05/03 07:21 AM
D
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
just get new microwave oven!

Re: Microwave Ovens? #135771
02/05/03 07:02 PM
02/05/03 07:02 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
It could also be a thermal cut-out operating. Sometimes restricted airflow will cause that if vent slots have become partially clogged or if a cooling fan isn't functioning properly.

Many of the latest designs use triacs on the control board to switch power to the u-wave power supply, heating elements etc.

The primary power circuits aren't usually too difficult to trace out -- Just a combination of thermal cutouts, microswitch interlocks and so on, although the exact arrangement can vary from model to model.

Many designs have three door switches, for example. Two are series interlocks, and the third is a "brute force" safety switch which puts a dead short on the supply to blow the fuse just in case the other two fail!

Re: Microwave Ovens? #135772
02/07/03 11:11 PM
02/07/03 11:11 PM
Trumpy  Offline
OP
Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Paul,
I think that you may have nailed it.
Airflow- never bothered to check the air routes through the appliance itself.
I only gave it a 5 minute once-over.
Microwave ovens do not use heating elements,
do they?, I thought it was only through microwave radiation, that the food was cooked. [Linked Image]

Re: Microwave Ovens? #135773
02/08/03 07:57 AM
02/08/03 07:57 AM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I was thinking of the fancier models which incorporate top and side quartz halogen heating elements for a "grill" and "browning" function.

Re: Microwave Ovens? #135774
02/10/03 12:37 AM
02/10/03 12:37 AM
Trumpy  Offline
OP
Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Oh,
OK Paul, just had me a wee bit confused.
No worries, though. [Linked Image]

Re: Microwave Ovens? #135775
02/14/03 12:44 AM
02/14/03 12:44 AM
Trumpy  Offline
OP
Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Paul,
You're the Man!!.
Have cleaned out all the air paths, given the unit a decent check over.
Hasn't missed a beat since.
Even heated my lunch up in it,
Thanks, mate! [Linked Image]

Re: Microwave Ovens? #135776
02/15/03 08:55 PM
02/15/03 08:55 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Glad you've solved the problem!

Just remember everyone, that the supply for the magnetron in a u-wave oven isn't to be trifled with: Typically 4 to 5kV at upwards of an amp. [Linked Image]

If the radiation don't get ya, then the EHT will! [Linked Image]

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