Help with amana microwave arching.

Hi,

For a couple of months I noticed that if I use Microwave while using Hood vent function I will get zapping sound from microwave. I just did not use those two functions together and it worked fine, but couple days ago it started doing it when I use only microwave function. It makes zapping sound for 2-3 seconds but eventually stops and heats the food.

Today I opened up the front of MW and checked out what was Arching. I need help with identifying what it is and where to get the part, and any other thoughts. My house is very old and I do not have ground, but MW worked fine for a year with no problems.

I have attached the picture.

Thank you

I'd just buy a new microwave or send it in for repair, sounds like a poor design. Also consider getting an electrician to install grounded outlets and GFCI outlets.

Thank you for reply. The Microwave is connected to GFCI outlet and it never gets tripped. I am out of warranty and was hoping I can just replace whatever component is broken. So far I identified that black (resistor, capacitor or whatever it is) thing is the problem. It is very accessible and I can just pull it out and plug a new one in. All I need is to know what it is so I can go to RadioShack and get it.

I am comfortable with soldering and working with electronics and know not to touch any other components, just it seems like an easy fix and I want to try it out before replacing the whole MW.

Thanks

The 'black thing' is the HV rectifier, you would need to get the proper replacement for a microwave (not a standard electronics part), but they are pretty well all the same, and interchangeable.

However, I've NEVER seen one arcing to the case, and I've been repairing microwaves for a few decades now.

You should also be VERY, VERY aware of the fatal voltages around that section, even with the oven unplugged the large silver capacitor can store enough voltage to kill you - and with it plugged in it's almost certain to kill you if you touch it.

You're unlikely to be able to buy the part at RadioShack, you need a supplier of microwave spares - and one that will supply the public (as an authorised microwave repair agent we're not allowed to sell spares to the public, or even non-authorised engineers).

Thank you for the reply. I uploaded the video of what happening on youtube. I do not know if you can even tell what the culprit.

https://www.youtube.com/watch?v=plW1r3lxikk&feature=youtu.be

I might just get another MW, I do not even know if anybody even repairs them anymore around here.

Does a GCFI outlet work without a ground?

blueroomelectronics said:

Does a GCFI outlet work without a ground?

Click to expand...

GFCI's installed without a ground will still work as designed for people protection but the "test" button on a three prong GFCI will not work because that type of test connects a 5mA bleed resistor between "line" and ground.


To boho:
reassemble and just toss the old oven away. I'm not being mean here, but if you are incapable of identifying the basic components and understanding the design, deadly voltages and currents inside that kind of appliance, you are playing Russian Roulette with a 6-shot revolver loaded with 5 bullets! Consider yourself damn lucky you haven't gotten a lethal zap or at the very least a debilitating zap of sorts.

Hi there,


I took a look at the video and although it is very impressive it does not tell us anything new because the camera aperture is too wide letting in too much light. So only you can see it clearly unless you use a very small aperture or dark filter.


But from what i can tell by viewing the still picture, you had two different problems and now you have one.

The first problem was that a couple of wires were too close and that caused arcing for a while. You probably fixed that problem when you moved the components apart much farther than they were before that.

The second problem is that you had carbon buildup from the previous arcing. This caused more arcing even once the components were moved apart more.

So the solution is to clean up the black part better such that you remove ALL the carbon. There is a chance that the case of this part was damaged in that the insulation properties of the body are not as good as they were before, so cleaning may not be enough. You could try removing as much carbon as possible and then coating it with some sort of electrical insulation coating, or possibly some fish paper loosely wound around the black body. It can be held in place with tie wraps, but be sure to allow ample space between the paper and black body so that enough air can get in to cool the device. You could even try placing a small section of a sheet (two or more layers perhaps) of fish paper between the two things that you said arc. Only you can see that clearly as i said.

How much would a new oven cost?


WARNING 1:
This can be very dangerous as others have pointed out. Ask Nigel about the proper way to discharge the cap before you work on it again if you dare.

WARNING 2:
When the cover is off your body and face area is subject to damage by flying parts that spring up from inside the oven where the parts are. Parts can explode sending very fast moving very hot parts toward your body or face. Safety glasses are a must if not more like a face shield.

OK, guys, the micowave put out a 3000 V near there. That's deadly material to play with.

It also gets kinda wierd to figure out the "what happened"? I see two possible scenereos:
1. the magnetron is breaking down and the diode overheated. Now it conducts to ground through the carbon tracks or whatever.
2. The capcitor is creating a high ripple current. Bad for everybody.

The fix, would be to 1) Not get killed in the process. 2) Replace the cap and diode remembering that there is 3000 V on it. 3) Do the water boiling test time in the microwave. 4) If it flunks, replace magnetron.

Reality: Replace Magnetron, cap and rectifier: $80, $20 and $10 USD respectively maybe.

HV servicing precautions must be in place. An V probe is always useful as well as a way to safely discharge the capcitor. Even after it's discarged, the voltage might come back. Yep, like magic. So, you really have to make sure it's gone. There is usually a resistor across the cap, that helps self-discharge the capacitor.

The diode is not likely the cause of the failure. The magnetron is likely the first hit. Magnetrons short. Filiments open, Easy tests. Diodes open and short - harder tests, need 10 VDC or more to turn on. DVM won't work. Capacitance tester may or may not work. Bad caps easy, partially bad, harder.

@Nigel - Do you have access to any Kenmore/Sanyo micro/convection manuals from the mid 80's?

KeepItSimpleStupid said:

@Nigel - Do you have access to any Kenmore/Sanyo micro/convection manuals from the mid 80's?

Click to expand...

We had a few Sanyo manuals, but we're in the process of moving to a much smaller workshop, and almost all the paper manuals are being disposed off - and the Sanyo microwave ones went the other month.

Darn: EM5525, 12360 control board. Now if you have a 12360 board, that would be cool.

KeepItSimpleStupid said:

Darn: EM5525, 12360 control board. Now if you have a 12360 board, that would be cool.

Click to expand...

We didn't have any Sanyo spares in stock, and (due to lack of space) we binned all the reclaimed Sharp microwave boards and magnetrons etc. I'd been saving.

Sorry to see your downsizing your 'shop nige.
Every so often I see flog off's of old valves and stock when tv repair centres move or sell up, good source of bits.

I think the blocking diode in the vid might not be flashing over to chassis, the diode itself might well have blown up due to having gone short and flashes over anode to cathode every time its powered up.

The blocking diode is actually a stack of diodes, the manufaturer will have spares but I doubt they will want to supply them, they understanably dont want customers poking around with 8000v or more.