From the beginning, I think mag went bad because oven started making a nasty clicking sound when hot & eventually blew the fuse. So I replaced mag.

Unit still don't work. New mag seems OK - no nasty noises.

Problem now: oven goes on briefly (30 sec), blows fuse, & shuts off.

So, an electrical tech used a meter on oven & said "bad diode."

Then, I replaced diode & fuse, same result, 30 sec quiet operation, then blows fuse, shuts off.

I noticed condenser don't spark when contacts are shorted as the instructions say to whenever working inside cover.

If mag was at fault in 1st place, could it have shunted the diode & shorted condenser?

Should I buy a new condenser? If so, now that I have started & run the unit with new diode installed, is the new diode ruined?

Thanks in advance,

Michael

Be very careful working with high voltage circuits. Microwaves circuits deliver 7KV In my experience a blown fuse can be 1, monitor switches being sticky, S/C Diode. These are the two switches that close when the door is closed. You see the two latches on the door, they are there so that microwave energy is not released with the door open. In your case the HV Diode fails something is drawing too much current. It could be the High voltage Capacitor (Condenser) There is not much in a microwave. The magnatron is a valve that emits hign frequency wave in (GHZ) Be careful with the HV Condenser as it could still hold charge out side of the oven.

Eng65

My sugeestion to you is to get rid of the defective oven ASAP as you have no idea if this unit is still safe to operate and you keep blowing fuses over and over again. They are cheap enough that you can dispose of this defective unit and buy a brand new one and not risk getting zapped or fried in the meantime. There is also a risk of overexposure to the rays if you somehow get the bad unit to stay on. Is this worth it? I say no. You could have a swell case of a housefire. Many firefighters have complained about do it yourselfers working on microwaves and they have to put the house fire out for them.

You made the wrong diagnosis. Magnetron issues are usually gradual or heating starts to decline.

The problem your describing is most likely a cap problem. The transformers operate in saturation and therefore it's not likely to blow out the diode. The transformer is essentially energy limiting.

The door switches will blow instantly, not 30 sec later.

The electrical tech needs to be fired. High voltage diode can have a 10V drop across them. When you buy a meter, you better know how to use it.

The magnetron was likely good.

Microwaves don't bother me. I've worked on 1KW RF transmitters, 30 KV at 1.5A and 100 KV at 0.1A power supplies and microwaves.

Eng65:
Your actually wrong in terms of the operation of the door switches. It's usually a combination of shorting and opening the power.

I know from my experience on working on them. My explanation of the electrical operation was adrift. The Monitor fuse does fail very often because the door becomes mis-alighned. The HV Transformer would blow the main fuse. They are dangerous to work on though even with a high voltage probe.

Regard,
Eng65

There is something that you have to be aware with high voltage capacitors. They will build up a charge by themselves. Big HV caps are usually shipped with a keeper ( a wire short actoss the terminals). 3 KV is about the minimum for the high voltage supply.

You said cap problem -- you mean the major condenser?

My major fear is that a minor component inside the unit is blown and I'll never be able to find it, but the major cap I found and removed.

It does not spark -- it should, shouldn't it?

[email protected]


You made the wrong diagnosis. Magnetron issues are usually gradual or heating starts to decline.

The problem your describing is most likely a cap problem. The transformers operate in saturation and therefore it's not likely to blow out the diode. The transformer is essentially energy limiting.

The door switches will blow instantly, not 30 sec later.

The electrical tech needs to be fired. High voltage diode can have a 10V drop across them. When you buy a meter, you better know how to use it.

The magnetron was likely good.

Microwaves don't bother me. I've worked on 1KW RF transmitters, 30 KV at 1.5A and 100 KV at 0.1A power supplies and microwaves.

Eng65:
Your actually wrong in terms of the operation of the door switches. It's usually a combination of shorting and opening the power.

You said cap problem -- you mean the major condenser?

My major fear is that a minor component inside the unit is blown and I'll never be able to find it, but the major cap I found and removed.

It does not spark -- it should, shouldn't it?

Michael


You made the wrong diagnosis. Magnetron issues are usually gradual or heating starts to decline.

The problem your describing is most likely a cap problem. The transformers operate in saturation and therefore it's not likely to blow out the diode. The transformer is essentially energy limiting.

The door switches will blow instantly, not 30 sec later.

The electrical tech needs to be fired. High voltage diode can have a 10V drop across them. When you buy a meter, you better know how to use it.

The magnetron was likely good.

Microwaves don't bother me. I've worked on 1KW RF transmitters, 30 KV at 1.5A and 100 KV at 0.1A power supplies and microwaves.

Eng65:
Your actually wrong in terms of the operation of the door switches. It's usually a combination of shorting and opening the power.

It seems that the door latch swiches may be the proble, First of all disconnect the 120v to the transformer leg and replace with an incadescanet lamp. Now the main fuse is took off and connect an incandescnet lamp. So when you turn on the microwve oven you could identify whether is the problem on the transformer and the high voltage cercuit. Connect the microwave oven to out let plug... if the incandescent lamp across the main fuse light fully that means bad door latch switch, because you not connected the main transformer so there is no way bad transformer,diode,or capacitor.