Self healing microwave

Just a little follow up. I’ve found a magnetron on-line that claims to be a substitute for mine (a 2M172J).

Tim

Seeing as the diagram for it "looks like a tube", the parametrics could be quite different. The HV transformer could be putting out a different voltage level, on the two designs.

Maybe the parametrics of your tube have shifted enough, it will start some times, and not others.

Paul

There's nothing like an intermittent fault to drive you round the bend.

Well, if it has been working correctly, then you are now guaranteed to have the HV capacitor(s) fully charged! If you do go fiddling around inside, perhaps to change the magnetron, you'll have to be really careful to make sure any caps are discharged completely.

I would very much doubt it.

One fairly simple thing to try if the fault's intermittent is to look for a dry joint. If the circuitry is reasonably straightforward, a few minutes going over any soldered joints with fresh solder can't harm.

Door switch trouble? I have never found a Magnetron to come back to life if it dies. More likely to be a dodgy connection. Also some silicon rectifiers of the vintage did have shrinking plastic syndrome where the wire that goes into the body gets a void around it and eventually the weld to the wire to the device inside can become intermittent. The only way to know for sure is to swap them out. Brian

I'm not convinced its the magnetron from your descriptions, sounds much more like a dodgy connection somewhere, be it a relay a switch dry joint or dodgy rectifier. Magnetrons tend to fade away, not just stop unless the standing wave detector finds microwaves coming back exceed a certain tolerable level of course. Brian

At that age it will be using leaded solder, so itswise to use the same or it might make things worse. Brian

Of course, Brian, *proper* solder! I've still got a few metres of the stuff for when it's required.

Should that phrase read "43 year OLD Toshiba"? I'm getting daily use from a Sanyo catering microwave oven of the same vintage (bought second-hand in 1986 when Isle College, Wisbech closed its catering course and sold off all the equipment).

Purely based on this one experience, my feeling is that if the magnetron has been working well for all these years, it's not going to be a magnetron problem now. Each time I've had a problem with my Sanyo, it's turned out to be related to a build up of dirt and/or grease. In one case, the dirt caused a problem with the connection to one of the big, internal fuses but the problems have usually been more of a mechanical nature and always (so far, fingers crossed, touch wood) fixable at home by myself.

Nick snipped-for-privacy@yahoo.ca

Its not illegal to sell it, just to use it in manufacturing

Tons for sale everywhere.

The point about lead free is its far harder to get it just right so it makes a decent joint. Amateurs are allowed to use tin/lead. As are some critical industries.

This. 2kV DC is no joke... especially due to 0.5*CV^2.

These caps are about 1uF, so about 2 joules of stored energy. At 2kV that could be a very nasty zap.

There is a heater element, which I suppose could do the light bulb thing, but seems unlikely. It could be insulation breaking down, either in the magnetron or capacitor.

Could be that too, although I wonder how it's managed to have a dry joint after 43 years. Could be cracking of joints from thermal expansion I suppose.

Theo

Well I’m a bit baffled as it’s working just fine now. It’s possible that something temporarily overheated but it was only being used for a bit of defrosting on a 50% duty cycle when it died so that seems unlikely.

Incidentally the suppliers of the compatible magnetron have confirmed that it *is* compatible so I’ll give that a go if and when it dies again.

Tim

Not true. Military and Civil planes still use leaded solder. Lead-free solder is not allowed according to my near neighbour who used to be a licensed aircraft engineer for Virgin.

Oh dear. You missed out the part of my post that said 'except for some industries'

I've seen no reason for it to b the magnetron, and would not replace bits at random. You might begin by hanging meters off the transformer to see if it still gets power when it goes faulty, and divide the fault area from there. It's a slow process when it doesn't fault often, and you must deal safely with the potential serious electrical hazards with doing this unsafely.