Daewoo microwave oven repair

[redwire]

The question is if microwave oven diodes are slow or fast recovery. They seem to all be fast-recovery, inverter use etc.

For the old B&W TV's and monitors, those HV rectifiers in a cartridge (really old are selenium stacks) I use a smaller fast-recovery diode like 2CL69 5mA 4-20kV but the 10-20kV parts 2CL77 need to be potted or it arcs across. If making a scope HV multiplier.
Microwave oven diode would likely work fine.

[eccerr0r]

I sure hope there aren't tv's using selenium rectifier stacks for crt rectification... More likely using selenium stacks only for "low" 200 volts and if that old, things like 1B3's for CRT final anodes.

[momaka]

Originally Posted by goodpsusearch

I don't know where this was stored, but the inside of the cooking chamber shouldn't rust like this. The oven doesn't look too old too to justify this level of oxidation.

I know, but unfortunately I've seen this quite often on my local classifieds with various modern microwaves (and occasionally some old ones too, but a lot more rarely - seems the old stuff are indeed better built/welded/painted.)

Originally Posted by sam_sam_sam

They used to sell special microwave paint for touch bad spots for inside the microwave shell

But I have not seen any for a very long time

Yeah, people just don't want to bother fixing anything anymore. A lot of things are getting too cheap to the point where it's cheaper / less effort to throw away the old/broken and buy new. And it seems more and more appliances make designs that are "not user-serviceable".

In regards to the touch-up paint... mine certainly needed more than just a few "touch-ups"

Originally Posted by redwire

Never seen rust in ovens, but habit is to leave the door open after cooking to air it out.

I suspect that's part of the reason why, too. Seems people just don't bother to clean up their spills and don't air out their MW when cooking something for very long nowadays. Otherwise, I doubt the relatively high humidity where I live (at least in the summer and parts of fall and spring) could do this kind of damage. After all, our MW is over 20 years old and still no signs of rust spots anywhere in the chamber. There are a few small ones starting to show up on the door where it bumps into the chamber (so I'm guessing the opening and closing of the door after all these years started these spots, and they eventually grew a bit... but still far from being anything significant.)

On that note, I grew up in Eastern Europe in the 90's, when getting a new appliance (especially a "Western" one like a microwave) was almost like a family celebration, lol. One of our more "wealthy" (at the time, anyways ) neighbors got a MW in the early 90's, and you bet they treated it with the utmost care.

But now? No one really cares, I think. Just use, abuse, and throw away when it's broken, then buy new again.

Originally Posted by eccerr0r

Considering that it costs $12 to mail something to my parents if it's 2 pounds and $18 if it got to $3, shipping heavy copper + laminated iron MOTs is part of the overall cost that shift towards transistors and flyback transformers...

Yup.
Well, it's a saving all the way around. Copper is getting more and more expensive - often to the point where it's cheaper to put several complex ICs and a complex overall design, just to save a little bit of copper in a transformer or wherever else. Of course, back when ICs and transistors (especially high-power ones) were expensive, it probably did make more sense to keep designs simple with less of these and more heavy passive parts. Just look at any wall adapter - despite having a few 10's of components and ICs, if not more, it's still cheaper than a regular iron-core transformer... and offers better regulation and lower standby consumption too (not to mention wide voltage input most of the time as well.)