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Grind Hard
10-12-2011, 12:52 AM
...it's a Sharp Carrousel II.

I was cooking two "chicken thangs" like I normally do when it just went "pop" and that was that. :eek: No magic smoke... no epic flashes, no arcing or sparking unless it was all internal. :confused:

Fuses down stairs are fine, if that was the problem the entire kitchen would have gone dark.

Tried a different outlet in another room... no response. Chicken thangs are still partly frozen. :rolleyes:

I know it says "no user serviceable parts inside" but really now... what are the odds that I popped something that could (say) be reset or repaired? I am a bit cautious about opening said microwave as I hear it has a GIGANTIC LIFE-ENDING CAPACITOR OF BLAZING ELECTRIC DEATH inside it.

Chris S.
10-12-2011, 12:56 AM
There's a flame proof ceramic fuse in there. Did it pop when you closed or opened the door or when you hit start?

Grind Hard
10-12-2011, 12:58 AM
It was running, about half way through the 5 min cook cycle.

Microwave is about five years old, and has cooked this particular meal dozens of times without issue.

macona
10-12-2011, 01:00 AM
Bad HV diode. Black block with one wire screwed to the case.

darryl
10-12-2011, 01:07 AM
It has popped an internal fuse. What could have caused it? Fuse getting old, door switches having sticking contacts, microwave tube shorting out. If you put in another fuse, it might be fine for years, or it could pop right away because it has problems. If you unplug it, it's safe to replace the fuse and try it again. Just don't touch the wires on the big metal can thingy. Chances are there's no voltage on them, since it dies off pretty quickly when power is interrupted, but no need to tempt fate anyway. The fuse area is totally safe to touch contacts or whatever, as long as the cord is unplugged. One dangerous thing in these microwave ovens is that the sheet metal they're made of has sharp edges, and there are ends of screws inside waiting to scratch you. Just pull the plug, open it up, and replace the fuse. If it blows again, you know there's a problem that needs fixing. It may not be worth it.

None of the several hundred microwave ovens I've gone through over the last year or so has a fuse on the outside, so you'll have to use your resistive heating appliance ( normal oven) for the chicken if you want to eat it any time soon- then you can start by removing the glass tray and everything inside that's loose, then see if you can find all the screws to take out so the cover will come off. There will likely be at least two screws on the bottom to take out, several on the back, maybe some on the sides, etc.

Grind Hard
10-12-2011, 01:12 AM
Chicken thangs have been fried into submission on the stove.

It is well after midnight here in Buffalo NY... I have plenty of other functional cooking devices I think I can put this in the project pile for the weekend.

Thanks to everyone for the advice.

lakeside53
10-12-2011, 01:21 AM
Yes, as mentioned - door switches - they are designed to blow the fuse if they malfunction, but several other components can do the same thing.

The last two I fixed (GE monogram) with blown fuses had a shorted HV capacitor in the magnetron circuit. The diode survived both times, but often it doesn't. Symptom - replace the fuse - the micro wave will light up - press cook - and it blows.

Take care if you are poking around in a microwave... if you are so inclined - this document covers A-Z.

http://www.repairfaq.org/sam/micfaq.htm#micmicgenp

wierdscience
10-12-2011, 01:42 AM
http://www.youtube.com/watch?v=MRp0DDidq5A

It's God's way.

DFMiller
10-12-2011, 02:42 AM
Before you rip into have you tried plugging it back in.
We have had at least two microwave shut down on thermal overload then continue to work for years without a burp. In fact our Maytag did just that in the last two days.
Dave

hemmjo
10-12-2011, 07:28 AM
I second the "try this first" repair tips. But, if that does not work and you decide to get a new one don't just throw it away. There are some nice magnets in it. Take it apart. Use a well insulated screw driver to short the capacitors. Then find the Magneton out and you find the magnets.

Microwave info >> http://www.gallawa.com/microtech/magnetron.html

Enjoy,

John

jugs
10-12-2011, 08:08 AM
It was running, about half way through the 5 min cook cycle.

Microwave is about five years old, and has cooked this particular meal dozens of times without issue.


It's bored it wants a change of diet & is having a temper tantrum :eek: :D

Chris S.
10-12-2011, 11:41 AM
As has been mentioned, sometimes the fuse just gets fatigued from constantly cycling. The fuse link actually flexes each time the Magnetron kicks on and relaxes when it turns off, which is often when the power setting is not at max. My last microwave used to blow them about every 4 months. It got to the point that I wished the cover had a zipper!

Chris

Grind Hard
10-12-2011, 11:51 AM
It's bored it wants a change of diet & is having a temper tantrum :eek: :D


This made me laugh. :D

lynnl
10-12-2011, 01:48 PM
Must be a microwave contagion making the rounds.

Yesterday morning I pulled the handle to open our microwave and the top end of the handle just pulled loose. No pop or crack, or anything signifying failure at that moment. The plastic had apparently broke the previous time it was used.

Then later in the day, having forgotten about that, I opened it again and succeeded in breaking the bottom attachment.

Superglued both ends back, which is holding so far. Fingers are crossed throughout the household. This is a built-in, above the stove, so replacement will be highly inconvenient.

DFMiller
10-12-2011, 01:52 PM
GB thanks for breaking my microwave with all your bad Karma. ;-)
I must report that the intermittent shutdown now seems to be a permanent fault on mine. it seems that if the door is closed its on.
Some further checking is required.
Unfortunately ours is mounted on the wall above the stove so I cant just replace mine with anything.

Last one lasted 15 years. This Maytag needs service after about 3.

Sign of the times.

I hope you have better luck.

Dave

jugs
10-12-2011, 02:10 PM
Superglued both ends back, which is holding so far. Fingers are crossed throughout the household.


Should be more careful when using superglue then :p :D

lynnl
10-12-2011, 02:14 PM
Should be more careful when using superglue then :p :D
Good eye! :D

I didn't notice the double entendre there. Tho it came close to being reality.

gary350
10-12-2011, 02:37 PM
I collect all the free microwaves I can get my hands on from craigslist. There is a fuse inside. Fueses are not all the same. There is 1 type none repairable fuse that looks like a .150" dia. stainless steel tube about .625" long. I usually solder a jumper wire across them. If you heard a pop then look for something that popped. Bad circuit board is 99% of the problem. The circuit board is nothing but a timer board. I have replaced circuit boards with a simple toggle switch and the microwave oven works fine only problem you turn it ON and it says ON until you turn it OFF. I have never found a bad magnetron tube. I strip them for parts and sell the parts on ebay a junk microwave is worth $75 in parts.

lynnl
10-12-2011, 02:45 PM
Probably works pretty good on Old Ladies and little kids too, huh?

You're just one charming fellow.

jugs
10-12-2011, 03:34 PM
************************************************** ****
.

Last edited by gary350 : Today at 07:26 PM.

I should think so :mad:

Consider your self lucky you dont live close to me :mad: :mad:

Arcane
10-12-2011, 05:13 PM
A few months back my microwave quit working. I decided to pop the cover off to check for anything I might be able to repurpose and found a small fuse had blown. It was just an ordinary 1 1/4 by 1/4 glass fuse so I replaced it and the unit has worked flawlessly ever since.

Chris S.
10-12-2011, 08:14 PM
There is 1 type none repairable fuse that looks like a .150" dia. stainless steel tube about .625" long. I usually solder a jumper wire across them.

So, let me get this straight... You're advocating this practice? :rolleyes: :eek:

gordob
10-12-2011, 08:35 PM
So, let me get this straight... You're advocating this practice? :rolleyes: :eek:

If he solders an appropriate Fuse wire as a jumper, Logic would think it would serve a similar purpose?

Not being a Sparky, i wouldnt know.

plastikosmd
10-12-2011, 08:50 PM
Code brown has a whole different meaning in the medical field

lakeside53
10-12-2011, 10:05 PM
I collect all the free microwaves I can get my hands on from craigslist. There is a fuse inside. Fueses are not all the same. There is 1 type none repairable fuse that looks like a .150" dia. stainless steel tube about .625" long. I usually solder a jumper wire across them. If you heard a pop then look for something that popped. Bad circuit board is 99% of the problem. The circuit board is nothing but a timer board. I have replaced circuit boards with a simple toggle switch and the microwave oven works fine only problem you turn it ON and it says ON until you turn it OFF. I have never found a bad magnetron tube. I strip them for parts and sell the parts on ebay a junk microwave is worth $75 in parts.


Pretty broad statement... "just a Timer Board". Maybe the old style MW, but today they also read the membrane keys, take sensor inputs and perform host of other features.

In my experience, dead magnetrons are pretty common. Logic board failures - rare, HV components in the magnetron circuits -common, door related fuse failure - common.

As for bypassing any safety feaures by insertion of a toggle switch, and soldering across a fuse (how about soldering IN a fuse?) ... no comment:rolleyes: Hope you have an understanding insurance company when someone sues you.


Ebay $75? Wow... unless it's a late model you can't get $25 for a used MW around here, and there are buckets of them.

Paul Alciatore
10-12-2011, 11:15 PM
From my experience, any and all of the components in a microwave can and do fail. Some more than others and that will depend on make and model.

Due to the high Voltage used, it is a bit dangerous to try to troubleshoot a microwave with the power on, so the best procedure is to unplug it BEFORE opening the case and test individual parts. Most of them can be tested with a simple VOM (Volt-Ohm Meter). Use a low Ohms scale for most tests below.

As others have said, most microwaves have a fuse and this can blow for no reason at all except old age. It can be tested with the Ohms setting on the VOM: continuity = OK and open circuit = bad. DO NOT bypass a bad fuse with a piece of wire. The fuse is there for a reason and if you bypass it, you may burn your house down. Get the RIGHT fuse or trash the microwave. You can buy a new one for less than $50 for gosh sakes.

There is a transformer and like all transformers, it can be tested just like the fuse. Check for continuity for each winding. Check for no continuity to the chassis. If it is bad, you will probably need to buy an original factory part and it will be expensive if you can even get one. Good luck.

Switches can also be continuity tested as above. Click On and unclick Off. Again, do not bypass a bad switch as this could create a dangerous situation, possibly allowing microwaves to exit the unit when the door is opened. You could get burned at the very least. Substitute switches should work OK if properly selected and installed. Of course, OEM would be best.

The rectifier can also be tested with a VOM. However, it may have several diodes in series which would cause it to have a higher forward Voltage. This means that a VOM that has only a 1.5 or 3 Volt battery may not be able to actually test it as the forward Voltage may be 6 Volts or more. Some better VOMs use higher Voltages for the higher Ohms scales and would be a better choice for this test. A diode or rectifier should read low resistance (Ohms) when measured in one direction and much higher resistance when the meter leads are reversed. If you see this differential, it is probably OK. If you see low resistance in both directions, it is bad. But if it measures high in both directions the test may be inconclusive due to the higher forward Voltage as explained above. If it is bad or if nothing else tests bad, you should replace it.

Timers come in two varieties, a circuit board or a mechanical timer. The mechanical timer can be easily tested with the VOM: continuity = OK and no continuity = bad. Circuit board timer/controllers are more difficult. Normally when they are bad, you will see no display and things like a beeper will not sound. But they can fail to activate the magnetron and still appear to operate normally. The only way to be completely sure it is supplying Voltage to the transformer (and hence to the magnetron) would be to measure the Voltage on the primary winding of the transformer with the unit in operation. I do not recommend this test for an electrical novice as there is grave danger of shock. Again, I would not be a big fan of replacing the timer with a simple switch as this may bypass all or some of the safety devices (switches, etc.) and you may wind up baking yourself. Do properly replace the timer if it is defective.

If all else is OK, you may have a bad magnetron. You WILL pay more for the magnetron than for a new microwave. I have a microwave that is built into my kitchen cabinets and I have replaced the magnetron in it twice. I have paid at least three times the original purchase price of the whole microwave oven for two replacement magnetrons. I did it to avoid the trouble and expense of a new custom installation. The only test you can perform on a magnetron is for filament continuity, again with the VOM and no power to the unit. Open filament = bad.

About all that remains is wires and plugs. Give them a visual inspection and test them with the VOM.

gwilson
10-12-2011, 11:22 PM
Our built in,not so old microwave suddenly decided to always turn itself on whenever the door was closed. This was not permanent,though. After several days it fixed itself.

Why worry about a countertop microwave? They are very cheap now. Our first one in the 80's was $450.00. Now what? $40.00?

gaston
10-12-2011, 11:29 PM
If one of my Wally world specials takes a dump, I scrap out and finish my whatever in the antique 30 year old "Pennys special" in the shop. just can't kill the old thing. built like a tank and I think weights as much as sir John's bridgeport!

J Tiers
10-12-2011, 11:45 PM
If properly designed-in, fuses do NOT EVER BLOW FROM "AGE".....

If they do, it is evidence of a lazy, ignorant, or not very thorough engineer. Or a purchasing agent who went for price alone.

There is an energy rating (I^2 * T) for any decent fuse , even from some of the questionable sources like Bel, etc. This shows the surge that the fuse will withstand without a problem. It INCLUDES the issues of flexing, etc, etc, etc.....

If you stay within the proper derate from that rating, the fuse will last hundreds of thousands of surges. If you mess up, it may last a dozen, or any number in between.

The easy way is to find the value that blows within 10 tries reliably. That is the fuse with surge rating equal to your surge...(pay no attention to current). Go to the appropriate surge rating of fuse that is current rated in the range you need. You may not find it in a given maker, and may have to use a different brand. The required rating will be a multiplier of the "threat" surge.

Look at the Littelfuse "fuseology" section , which should be on their website, as well as in catalog. You will see the multiplier that corresponds to any lifetime in turn-on surges.

Grind Hard
10-12-2011, 11:46 PM
I have a new microwave now. Splurged and got an ultra-deluxe one.

Going to take the other one apart and either build a portable short-range EMP generator or some kind of radar-jammer/cloaking device for my car.

Either way I expect to be either dead or in prison by this time next week.... possibly horribly mutated as well.

Chris S.
10-13-2011, 12:04 AM
If he solders an appropriate Fuse wire as a jumper, Logic would think it would serve a similar purpose?

Not being a Sparky, i wouldnt know.

The AWG of the jumper was not specified. A reader could interpret that to be any wire gauge. I could go on, chapter and verse, as to why this is a bad idea but lets just start with a basic one...

Wire, any wire, is not recognized by ANSI, NEMA or UL as fuse. If the microwave catches fire and the house suffers damage, what do you think the fire dept and the insurance company's reaction is going to be when they discover a wire where a fuse should be? Do you think the insurance company is going pay off or call this gross negligence?

Nothing in the realm of electronics is basic or simple. Every component has a data sheet associated with it, even a lowly fuse, as you can see here.

http://www.belfuse.com/Data/Datasheets/3AG.pdf

Grind Hard
10-13-2011, 12:11 AM
Relax folks... I am smart enough NOT TO BYPASS A FUSE.

This is common sense. At least to me.

Thanks for the suggestion but my "chicken thangs" are not worth risking a housefire over!! :)

Chris S.
10-13-2011, 12:18 AM
Code brown has a whole different meaning in the medical field

Sounds like you work or worked in this field. How many "Code Strong's" do you average per month? :D

Chris

Grind Hard
10-13-2011, 12:31 AM
Code Brown means a shooting in progress at Wal-Mart. That and Code Red are the two you never want to hear over the PA system.

darryl
10-13-2011, 03:40 AM
Hmm- what to do with an old microwave oven. Assume you can get it to work, and that you pull the magnetron and wire it up as a hand-held 'emitter'. Hmm, maybe it could first be tested on a smart meter-