With microwaves retailing for under $100 just pitch it and buy new.

Point well taken.

However, it is known that the fuse has only blown.

What is the cost of a fuse? Less than a dollar.

Had the item required replacement of a major part (and hence substantial cost) I would definitely have gone for your suggestion.

Well you just may have that if you replace a 8 amp fuse with a 10 amp fuse. With all the sources available even the manufacture an 8 amp fuse should be easy to acquire. With out better info on the type here is listing for fast acting http://www.mcmaster.com/#71385k33/=4ct9lu

By the same token, as you seem well enough informed about the dangers and consequences, Why not just put the 10A in and see if it works? Keep an eagle eye on it the first few times you turn it on and make sure you don't burn down the house, I would think 10A would be no problem, and if it is we've already established that a new one is relatively inexpensive.

My concern would be that yes "it is that the fuse has only blown" but what caused that? maybe a fluctuation in line voltage, but more likely something else internal drew too much amperage, and even the 10A will blow quickly I surmise.

Best of Luck

-T

I would not do it. Try a Slow Blow 8A fuse same current rating but can handle transient current surges.

Nuked any aluminum foil recently? You may have blown the fuse when the magnetron moded. Don't use a slow blow if you may do it again, the fuse is fast blow for a good reason -- protect something much more expensive. Or maybe the mag is getting a little flaky. You'll know when that fuse goes again if it ever does. If the fuse is as tight rated as 8A vs 10A it may well have just failed of too many thermal cycles at high dv/dt. Go with the 10A fast blow, 50% more power at failure probably will just make your final decision that much easier.

8A 250v = $1.37 buy a new micro for that!

The blowing of a fuse is not a trivial event - something operated at way over it's safe limit.

Google this: 8A 250V

It will give you lots of suppliers for the correct fuse.

You are dealing with very high voltages and microwave power levels - nothing that is safe to test to destruction.

If replacing the blown fuse with the correct fuse doesn't help, it is time to give an appliance repair guy a few bucks.

Going from an 8 to a 10 amp fuse should not be encouraged but as someone already pointed out, Microwaves are getting cheaper to purchase all the time. This one is likely out of warranty or you'd likely have someone else fix it at their expense.

On the other hand, if you are a regular here, you probably enjoy the challenge that comes with fixing things, which is probably why you're poking around in the guts of that MW.

Resistance from oxidation does cause an increase in operating temperature in the fuse holder. Combine that with the effects of time and it could well turn out that all you need is a new fuse and to clean the fuse holder with a wire brush.

I was surprised how much dust, grime and foreign matter had accumulated in the electronics section of my MW. A bit of cleaning with some compressed air will likely help too. If the magnetron or its power supply have reached the end of their life, then there's not much point in going any further.

I found diagnostic charts and trouble shooting guides on the Internet. Not just generic test procedures but make and model specific values as well.

One thing to be mindful of is that they are placed inside a shielded cage for good reason. The power supply is a high voltage unit, similar to what used to be found in the B+ of large picture tubes and of course microwaves are not the sort of things you want bouncing around inside your insides.

Mine was not worth repairing so I stripped the Magnetron and saved the magnet. Wow, these are not your grand pa's magnets!

It's safe if you are careful but please, be appropriate!

L.J.

This one is only 1.5 years old. But I never thought of going in for a service guy as I wanted to tinker with it myself. After checking the other circuit components and based on the various excellent feedbacks from the CR4 members I went in for the 10Amp fuse. Before switching it on I was having a good look at the MW and there I noted that the path from where the microwaves come out might have been blocked by small cockroaches as one or two of them were moving inside. It is my feeling that this blockage could have resulted in high build up of back emf resulting in fuse failure. Just a guess.

I plan to switch it on today and see what happens.

I don't see a big issue with a 10A fast acting fuse but I like the idea of the 8A slo blo better. Odds are either will simply open again when the problem with the microwave strikes again.

You might put an ohmmeter between the microwave side of the fuse and ground to see if the unit is shorted to ground before you bother. If you're reading zip ohms I would just get a new microwave.

I searched all over for an 8 amp fuse with no luck. Then my wife suggested looking at the auto parts store. They have electrical equipment for all kinds of old cars, or they can get it quickly. I didn't find 8 amp, but I did find a box of 7.5 amp. Close enough for me.

Panasonic microwave ovens of that vintage are built around inverters as a HV source and they invariably fail after a few years.

I would put a 10A glass fuse in plug it in turn it on and see what happens. If it blows in a spectacular fashion it could be a monitor switch that is normally closed when the door is open and may not open when you close the door, there are some other possibilities too. If the microwave comes on and shuts down after a few sec it's inverter. In any case if you're not familiar with how to repair it (and it seems to be a case), I would close it and take it to a 'microwave guy'.

Join Freecycle.com they give away Microwaves on there all the time.