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?.

sounds like a software / firmware error.

Replace PCB logic board..

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.
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).]

just get new microwave oven!

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!

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.

I was thinking of the fancier models which incorporate top and side quartz halogen heating elements for a "grill" and "browning" function.

Oh,
OK Paul, just had me a wee bit confused.
No worries, though.

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!

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.

If the radiation don't get ya, then the EHT will!

Paul,
That's a really good point!.
I use neoprene covers over the EHT part of the microwave, when I'm working on them.
I remember making a Jacobs Ladder out of a microwave oven supply and a few other bits,
and it worked well, until the ladder wires shorted together.
Won't be building one of them again, for a while, anyway!.

There have been quite a few Tesla Coil projects in the American electronics press in recent years, as well as companies marketing kits for Jacobs ladder type experiments.

Hey Paul,
Do you know of any good sites on the Tesla Coil, I have been looking to build one of these.
Can you help?.

Trumpy:
Try these for a start: www.webring.org/cgi-bin/webring?ring=TeslaRing&list
www.amasci.com/tesla/tesla.html

Just let us know how it goes

[This message has been edited by cubby964 (edited 02-18-2003).]

Also check out:
www.pupman.com

Thanks for the links, Guys.
Will check them out!.

Trumpy,

I came across this fellow who is a Microwave Technician (I think). Maybe he can help you after he gets done with his coffee break.




Bill

[This message has been edited by Bill Addiss (edited 02-19-2003).]

Bill,
Now, that is flash, mate,
Love a good joke like that.
We need more of this sort of humour at ECN,
we all love a laugh, just takes the doom and gloom away from the working day!.
Just a shame, I haven't got a Digital Camera,
for submitting offences, of course!.

Trumpy,

I was at an Amusement Park the other day and saw this character on display from the movie Men In Black and thought of this Thread.


Bill

Bill, your photo reminded me of this "real" urban folklore... www.snopes.com/horrors/techno/micropet.htm

BJ,

You really have to watch those old Ladies I guess. They've been doing things to Pets for over a hundred years and still haven't learned anything!


Bill

[This message has been edited by Bill Addiss (edited 02-21-2003).]

My God,
Bill, they've managed to shrink a Lady, down to near Microwave size!.
What's next?, the CD sized Lady?.