A big, 20 year old, quality microwave went kaput.... I think. Convection,
all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough about
them to fool with them safely. Mebbe I'll give it to my neighbor's kid....
No, No, just kidding..... lol
--
EA

On Friday, January 4, 2013 6:24:48 PM UTC-6, Existential Angst wrote:
A big, 20 year old, quality microwave went kaput.... I think. Convection,

all the bells/whistles, GE.

Anything worth salvaging, of diy-er value?? The klystron is proly too

dangerous to fool around with, but man, what a honkin xsformer in there.

What's the secondary? Klystrons need such xsformer poundage??



I have the working innards of another microwave, but don't know enough about

them to fool with them safely. Mebbe I'll give it to my neighbor's kid....

No, No, just kidding..... lol

--

EA

The outer coils ( high voltage windings) will strip off easily leaving a primary and core you could add a few turns to for a spot welder supply...

On 1/4/2013 4:35 PM, Cross-Slide wrote:
On Friday, January 4, 2013 6:24:48 PM UTC-6, Existential Angst wrote:
A big, 20 year old, quality microwave went kaput.... I think. Convection,

all the bells/whistles, GE.

Anything worth salvaging, of diy-er value?? The klystron is proly too

dangerous to fool around with, but man, what a honkin xsformer in there.

What's the secondary? Klystrons need such xsformer poundage??



I have the working innards of another microwave, but don't know enough about

them to fool with them safely. Mebbe I'll give it to my neighbor's kid....

No, No, just kidding..... lol

--

EA

The outer coils ( high voltage windings) will strip off easily leaving a primary and core you could add a few turns to for a spot welder supply...

Don't forget to take out the magnetic shunts.

Transformer $0.34/lb

On 2013-01-05, Existential Angst wrote:

A big, 20 year old, quality microwave went kaput.... I think. Convection,
all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough about
them to fool with them safely. Mebbe I'll give it to my neighbor's kid....
No, No, just kidding..... lol

http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

"Bob Engelhardt" wrote in message
...
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

Ossum.

Re the possible very high xsformer temps:
Mebbe that's part of the convection oven feature?? LOL

Why the side-by-side coil design?
What do you think of CrossSlides idea of making a spot welder ditty?
--
EA

On 1/5/2013 3:50 AM, Existential Angst wrote:
"Bob wrote in message
...
http://www.mwdropbox.com/dropbox/FunWithMOTs.pdf

Ossum.

Re the possible very high xsformer temps:
Mebbe that's part of the convection oven feature?? LOL

Why the side-by-side coil design?
Easier/cheaper to wind.
Better high voltage isolation.
Magnetic shunts decrease the coupling so the output impedance is higher.

What do you think of CrossSlides idea of making a spot welder ditty?

Lots of info on the web about doing so.
I tried to use one as a battery tab welder.
Used a cycle counter synchronized to the line to provide constant output
and thwart saturation.
On a good day, it worked great. But they're very sensitive to resistance
in the weld path. Repeatability sucked.

Got MUCH better repeatability with a CD welder.

If you're just trying to heat stuff up red hot, shouldn't have
that much problem with repeatability.

On 1/5/2013 6:50 AM, Existential Angst wrote:
...
What do you think of CrossSlides idea of making a spot welder ditty?

http://www.mwdropbox.com/dropbox/MOT...rPrintable.pdf

It was a lot of fun making it, but I haven't used it that much. For the
stuff that I do, a MIG-ed plug weld is often more convenient, faster,
easier.

Bob

On 1/5/2013 6:34 AM, Bob Engelhardt wrote:
On 1/5/2013 6:50 AM, Existential Angst wrote:
...
What do you think of CrossSlides idea of making a spot welder ditty?

http://www.mwdropbox.com/dropbox/MOT...rPrintable.pdf

It was a lot of fun making it, but I haven't used it that much. For the
stuff that I do, a MIG-ed plug weld is often more convenient, faster,
easier.

Bob
Nice job.

A couple of points for newbies.
All solid state relays are not created equal.
If you can, get one that turns on at zero crossings.
Reduces transients. Ask me how I know ;-(

Second, although your reasoning for series primaries
is spot on...newbies might be tempted to experiment.
You can put the primaries OR the secondaries in parallel.
With dissimilar transformers you won't be able to get the
turns ratios exact, so paralleling both might result in
a shorted SS relay and a PANIC while you try to get it
unplugged. All that humming and smoking can be distracting.

While it's certainly possible to build this stuff without any
instrumentation, it's always a good idea to verify what you're
doing.
I was working with 120VAC. I reworked my secondary circuit
to take out two milliohms.
Welds got better.
Didn't discover till I measured it later that I was sucking
over 40A out of a 15A circuit. Was only for four cycles, but
it's
not something I want to do.

Seemingly inconsequential changes in the secondary path can
significantly affect the primary current. The math is simple,
but it's easy to overlook. Dealing with thousands of amps
is outside the experience of many of us.

On Fri, 04 Jan 2013 19:24:48 -0500, Existential Angst wrote:

A big, 20 year old, quality microwave went kaput.... I think.
Convection, all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough
about them to fool with them safely. Mebbe I'll give it to my
neighbor's kid.... No, No, just kidding..... lol

Secondary voltage is around 1000V. It's perfect for, well, a microwave
oven. Not much else, though -- they're kind of optimized for the job
they do (see Mike's comments about the shunt).

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Shucks, I have tubes that run that all day long.

But I'm not running TV or radio tubes.

The secondary is easily cut off many of the designs.
It is normally replaced with a high current few turn
winding. As in the spot welder. Or destructive fuse tester. :-)

I have a 22 amp 5v transformer that I use to heat the filaments
of high current thyatrons.

Martin

On 1/5/2013 10:18 AM, Tim Wescott wrote:
On Fri, 04 Jan 2013 19:24:48 -0500, Existential Angst wrote:

A big, 20 year old, quality microwave went kaput.... I think.
Convection, all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough
about them to fool with them safely. Mebbe I'll give it to my
neighbor's kid.... No, No, just kidding..... lol

Secondary voltage is around 1000V. It's perfect for, well, a microwave
oven. Not much else, though -- they're kind of optimized for the job
they do (see Mike's comments about the shunt).

On Jan 4, 6:24*pm, "Existential Angst" wrote:
A big, 20 year old, quality microwave went kaput.... *I think. *Convection,
all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? * The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? *Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough about
them to fool with them safely. *Mebbe I'll give it to my neighbor's kid.....
No, No, just kidding..... * lol
--
EA

"..but don't know enough about them to fool with them safely."

Rule #1...microwave ovens generate high enough voltage to
kill...easily.

If you really do not know how to deal with high voltage electronics,
you really should not be inside a microwave oven.

If you do have the working knowledge, most of the oven can be reused
as parts for other projects.

TMT

On Jan 4, 5:24*pm, "Existential Angst" wrote:
A big, 20 year old, quality microwave went kaput.... *I think. *Convection,
all the bells/whistles, GE.
Anything worth salvaging, of diy-er value?? * The klystron is proly too
dangerous to fool around with, but man, what a honkin xsformer in there.
What's the secondary? *Klystrons need such xsformer poundage??

I have the working innards of another microwave, but don't know enough about
them to fool with them safely. *Mebbe I'll give it to my neighbor's kid.....
No, No, just kidding..... * lol
--
EA

Not klystron, magnetron. There are two donut ceramic magnets on the
magnetron, sizes vary, but have fairly hefty pulls. Can be re-
purposed for a lot of things. Have one on the 4x6 gearbox as a
particle trap and wrench holder, slap one on the drill press head to
hold the chuck key, I use any number of them for the maggie-in-a-
baggie trick for picking up steel shavings. Newspaper bags are long
enough I don't have to bend over. Useful for a bunch of things. My
dad used a bunch of them for holding a windshield cover on during the
winter, saved a bunch of scraping after snow storms.

If you feel destructive, you can pull the magnetron apart. There's a
solid copper puck with a bunch of holes in it that could go as copper
scrap.

Usually is a small motor or two, one for the stirrer at the top,
another for the turntable at the bottom. If it had a convention oven
feature, there's a heater element, controls for same, blower/fan.

Only gotcha is that there's a HV cap somewhere in there, put a
screwdriver across the terminals(insulated handle, of course) just to
make sure it's discharged, then pull it. The unit is now defanged.
Cut the cord off the unit.

Stan

Stanley Schaefer wrote:

Not klystron, magnetron. There are two donut ceramic magnets on the
magnetron, sizes vary, but have fairly hefty pulls. Can be re-
purposed for a lot of things. Have one on the 4x6 gearbox as a
particle trap and wrench holder, slap one on the drill press head to
hold the chuck key, I use any number of them for the maggie-in-a-
baggie trick for picking up steel shavings. Newspaper bags are long
enough I don't have to bend over. Useful for a bunch of things. My
dad used a bunch of them for holding a windshield cover on during the
winter, saved a bunch of scraping after snow storms.

If you feel destructive, you can pull the magnetron apart. There's a
solid copper puck with a bunch of holes in it that could go as copper
scrap.

Usually is a small motor or two, one for the stirrer at the top,
another for the turntable at the bottom. If it had a convention oven
feature, there's a heater element, controls for same, blower/fan.

Only gotcha is that there's a HV cap somewhere in there, put a
screwdriver across the terminals(insulated handle, of course) just to
make sure it's discharged, then pull it. The unit is now defanged.
Cut the cord off the unit.


Some microwave oven Magnetrons have a high temp ceramic made with
Berilium Oxide. They are safe as long as you don't do anything stupid
and turn it into dust. If you do, it can kill you.

On Sat, 05 Jan 2013 08:12:43 -0800, mike wrote:

On 1/5/2013 6:34 AM, Bob Engelhardt wrote:
On 1/5/2013 6:50 AM, Existential Angst wrote:
...
What do you think of CrossSlides idea of making a spot welder ditty?

http://www.mwdropbox.com/dropbox/MOT...rPrintable.pdf

It was a lot of fun making it, but I haven't used it that much. For the
stuff that I do, a MIG-ed plug weld is often more convenient, faster,
easier.

Bob
Nice job.

A couple of points for newbies.
All solid state relays are not created equal.
If you can, get one that turns on at zero crossings.
Reduces transients. Ask me how I know ;-(

Second, although your reasoning for series primaries
is spot on...newbies might be tempted to experiment.
You can put the primaries OR the secondaries in parallel.
With dissimilar transformers you won't be able to get the
turns ratios exact, so paralleling both might result in
a shorted SS relay and a PANIC while you try to get it
unplugged. All that humming and smoking can be distracting.

While it's certainly possible to build this stuff without any
instrumentation, it's always a good idea to verify what you're
doing.
I was working with 120VAC. I reworked my secondary circuit
to take out two milliohms.
Welds got better.
Didn't discover till I measured it later that I was sucking
over 40A out of a 15A circuit. Was only for four cycles, but
it's
not something I want to do.

Seemingly inconsequential changes in the secondary path can
significantly affect the primary current. The math is simple,
but it's easy to overlook. Dealing with thousands of amps
is outside the experience of many of us.

40A for under a tenth of a second is well within the capacity of a 15A
residential receptacle circuit. A 20A circuit would be better, but
15A works as long as you keep the duty cycle within reason - Go look
at the start surge of a refrigerator compressor sometime.

A fridge might pull 60A to 90A of Locked Rotor current for that same 4
cycles till the motor starts turning, then it ramps down as the motor
spins up to the usual 2A run current.

Much more dramatic for a 5-Ton AC - this is why they never go that big
on an RV and put two small units. You can't get that much start surge
out of the average generator set and it'll stall out. But two smaller
roof AC's that are deliberately stagger started, that works.

-- Bruce --