Transplant a microwave oven guts ?

Thread Starter

Externet

Joined Nov 29, 2005
2,236
Hello all.
My year old microwave oven died. As it has a feature I prefer to any other, would like to resurrect it canibalizing another oven. Has anyone done it ?
It is a cheap vulgar medium sized 1000W and by choosing a donor of about the same power; I think a transplant of magnetron + transformer should suffice. Opinions ?
Symptom was loud mechanical vibration and not heating. Its 0.85 A HV secondary blown fuse replaced. Same with some burn smell :confused:.
 

BobTPH

Joined Jun 5, 2013
9,177
I wouldn’t try anything like that until I was certain of the root cause of the failure. You risk just blowing another transformer and magnetron.
 

dendad

Joined Feb 20, 2016
4,496
I would assume you do have the experience, but I feel this is worth saying maybe for others who may read this posting.

I would advise you to be very careful, lethal voltage and radiation are in that box!
Now that is out of the way, try disconnecting the mains from the magnatron transformer and ensure the timer and turntable still work ok.
Next, reconnect its transformer primary but disconnect the secondary windings and see it it runs without the rumbles. If so, the transformer may be ok.
Then, reconnect the secondary windings but leave the magnatron disconnected. If the vibration returns, it may be the EHT rectifier stack and/or the filter capacitor.
Just remember there will very high volts there even after it is turned off,

If they control stuff works ok, it should be possible to transplant the power works from another oven if it mechanically fits ok. Pay particular attention to the magnatron mounting as it is a good idea to keep the microwaves in the oven!
If you do not feel you have enough experience to do this, don't!
We tend to want to keep those who post here, not to have them fry themselves.

Oh, just for interest, here is my mod for a microwave oven...
https://www.thingiverse.com/thing:5263579
 
Last edited:

Pyrex

Joined Feb 16, 2022
294
hi
first of all, check high voltage diode and capacitor. Use a megger at 2,5kV or at 1kV.
Disconnect wire from HV winding and start the microwave. If transformer is OK, no hum at all when it is powered.
If everything is OK, magnetrone is faulty. It is not so easy to found a donor, as they are different, power rating is not helpful in this case.
Nevertheless, in most cases the magnetron itself is found OK, small capacitors often found shorted. Those ceramic capacitors are located in the metal box where magnetron heater is wired
 

Thread Starter

Externet

Joined Nov 29, 2005
2,236
Thanks. The transformer gets 120VAC fine at its primary from the healthy control board and relays. Will not attempt to measure secondary; do not have a KV meter. Will not buy a megger for other tests. There is no vibration noise, no heating.
Plan is to replace the magnetron first; if not, continue to capacitor, diode, transformer. Am aware of risks and precautions.
 

ApacheKid

Joined Jan 12, 2015
1,658
Thanks. The transformer gets 120VAC fine at its primary from the healthy control board and relays. Will not attempt to measure secondary; do not have a KV meter. Will not buy a megger for other tests. There is no vibration noise, no heating.
Plan is to replace the magnetron first; if not, continue to capacitor, diode, transformer. Am aware of risks and precautions.
Keep away from this, the voltages from the secondary of those transformers are perhaps the most dangerous electrical systems in your home. There are videos on youtube that explain the lethality of these, just get a new oven, nothing good about messing around with this.
 

ThePanMan

Joined Mar 13, 2020
801
My year old microwave oven died.
Only the good die young.

If the old unit has a feature you want to keep and you know the control board is good try taking a working machine and Frankenstein the control board into the working machine. Personally I'd stay away from the high voltage. One wrong move and you're de--------------.
 

Tonyr1084

Joined Sep 24, 2015
7,964
I've scavenged a couple control boards from old ovens. I currently use one for the clock feature. As for the output relay, I've hooked that to a 120VAC 15A duplex outlet. I can turn the outlet on for up to 99 minutes and 99 seconds. Primarily I use that feature to control my soldering iron. Far too often I leave it idling with a hot tip for hours. If I need to do some soldering and I think it'll take me no more than 20 minutes I'll set the cook timer for 20 minutes. With the soldering iron plugged in - it will shut off after 20 minutes. If I need a few more minutes I can hit the [ADD MINUTE] button as many times as needed to keep the iron hot. If I forget, which I do from time to time, the iron shuts off.
 

Thread Starter

Externet

Joined Nov 29, 2005
2,236
Only the good die young ? Still have a good 75 pounds old Amana Radarange from ~1969 that has not died yet, as vintage-in-reserve working fine
:)

1706459829782.png


The feature I like from the one failed is stainless steel interior. And all the rest too.

Hi Tony. Me too, transplanted a timer from a defunct microwave oven to an oven/toaster and been great for 10+ years; have not burned out the house forgetting it is on.
 

MisterBill2

Joined Jan 23, 2018
19,045
Many years ago I did a transplant of the magnetron from a microwave oven with a failed control board to one with a failed magnetron. It worked out very well. So if it is a tube failure then I predict success. Just be very careful to get the tube connections the same. You should not need to swap any other parts, is my guess. So it is probably not any need to swap the transformer or even the diode. But be careful to note which way the diode points in case that is the failed item. And leave them both unplugged for a few hours before even opening the case. And be sure to replace all of the case screws when you re-assemble.
 

Hymie

Joined Mar 30, 2018
1,288
If you don’t have a microwave leakage meter to hand once you’ve got it working, test for leaking microwave energy using a grape on the end of a toothpick.

Run the grape along the door edges and any other areas you suspect might be leaky – the grape should remain cold, indicating little or no microwave leakage.
 

MisterBill2

Joined Jan 23, 2018
19,045
After a magnetron transplant, replacing the steel case should prevent any external energy leakage. THAT is why I suggested being sure to replace all of the screws.
Those who disagree are welcome to remove the door and bypass the interlock switches so as to make loading and unloading more convenient. But the heating effectiveness inside the oven may be reduced a bit.
 

michael8

Joined Jan 11, 2015
421
My microwave blew it's fuse and the replacement fuse. I found out that the HV capacitor said 4 uF but measured 4 ohms. A replacement "borrowed" from a different microwave worked fine.
 
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