I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this unit?

Thanks!

John
AB8O

I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this unit?

Thanks!

John
AB8O

Off the top of my head.......

The HV transformer. Output 1 to 2KV at several hundred to a thousand KVA

HV capacitor 1 to 2+ uF at several KV

HV diode. several KV PRV.

Magnetron..... I don't know what I could do with them, but I keep them
anyway. Maybe if I ever get into plasma physics, or building my own fusion
reactor, I'll be set.

A thermal limit switch that is mounted on the magnetron.

A set of large magnets that is mounted around the magnetron. The outer
magnetron casing can usually be disassembled to remove them. They can be
used to make generators and the like.

If you do remove the magnets from the magnetron, don't throw away the actual
magnetron tube. With out the magnets, it acts like a normal vacuum tube
diode. with a PRV of several KV, and a peak cathode current of up to an amp,
a pare of them would work good in a HV power supply. Filament voltage is
usually a couple volts at a few amps.

Several NO switches on the door for safety interlocks, and timer control.

A relay, or high power triac for controlling power to the transformer and
magnetron.

A light bulb that lights the inside of the microwave.

A fuse or two. Will save you a trip to town if you have another project that
blows a fuse at an inopportune time.

Sometimes a smaller transformer with about 4 to 12V ac output for powering
the timer/display.

If you are into getting the last drop out of a salvage mission, then you can
usually get a moderate number of transistors and diodes off the
timer/display board.

The only problem I have found with doing the last thing on the list, is you
tear the microwave apart, then the last thing you do is go after the timer
board. When you get done pulling all the parts off of it, and you test them
to find out what they are. (NPN, PNP........) you find one that is
bad.......... Then it hits you........That component ran the this and
that....... That bad component is why the microwave wasn't working.......
Then you have to decide if it is worth putting it all back together after
you find out what died........ I usually don't.

N9WOS wrote:
I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this
unit?

Thanks!

John
AB8O

Off the top of my head.......

The HV transformer. Output 1 to 2KV at several hundred to a thousand
KVA

HV capacitor 1 to 2+ uF at several KV

HV diode. several KV PRV.

Magnetron..... I don't know what I could do with them, but I keep them
anyway. Maybe if I ever get into plasma physics, or building my own
fusion reactor, I'll be set.

A thermal limit switch that is mounted on the magnetron.

A set of large magnets that is mounted around the magnetron. The outer
magnetron casing can usually be disassembled to remove them. They can
be used to make generators and the like.

If you do remove the magnets from the magnetron, don't throw away the
actual magnetron tube. With out the magnets, it acts like a normal
vacuum tube diode. with a PRV of several KV, and a peak cathode
current of up to an amp, a pare of them would work good in a HV power
supply. Filament voltage is usually a couple volts at a few amps.

Several NO switches on the door for safety interlocks, and timer
control.

A relay, or high power triac for controlling power to the transformer
and magnetron.

A light bulb that lights the inside of the microwave.

A fuse or two. Will save you a trip to town if you have another
project that blows a fuse at an inopportune time.

Sometimes a smaller transformer with about 4 to 12V ac output for
powering the timer/display.

If you are into getting the last drop out of a salvage mission, then
you can usually get a moderate number of transistors and diodes off
the timer/display board.

The only problem I have found with doing the last thing on the list,
is you tear the microwave apart, then the last thing you do is go
after the timer board. When you get done pulling all the parts off of
it, and you test them to find out what they are. (NPN, PNP........)
you find one that is bad.......... Then it hits you........That
component ran the this and that....... That bad component is why the
microwave wasn't working....... Then you have to decide if it is
worth putting it all back together after you find out what
died........ I usually don't.

Good list we could add:
hardware (screws, washers etc)
mains power cord
some models have motorized wave "stirring" or magnetic drive platter turners
keypad for PIC projects

All in all, there's allot of good stuff in one. I shouldn't have thrown my
old one out.

Anthony Fremont wrote:
N9WOS wrote:
I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this
unit?

Thanks!

John
AB8O
Off the top of my head.......

The HV transformer. Output 1 to 2KV at several hundred to a thousand
KVA

HV capacitor 1 to 2+ uF at several KV

HV diode. several KV PRV.

Magnetron..... I don't know what I could do with them, but I keep them
anyway. Maybe if I ever get into plasma physics, or building my own
fusion reactor, I'll be set.

A thermal limit switch that is mounted on the magnetron.

A set of large magnets that is mounted around the magnetron. The outer
magnetron casing can usually be disassembled to remove them. They can
be used to make generators and the like.

If you do remove the magnets from the magnetron, don't throw away the
actual magnetron tube. With out the magnets, it acts like a normal
vacuum tube diode. with a PRV of several KV, and a peak cathode
current of up to an amp, a pare of them would work good in a HV power
supply. Filament voltage is usually a couple volts at a few amps.

Several NO switches on the door for safety interlocks, and timer
control.

A relay, or high power triac for controlling power to the transformer
and magnetron.

A light bulb that lights the inside of the microwave.

A fuse or two. Will save you a trip to town if you have another
project that blows a fuse at an inopportune time.

Sometimes a smaller transformer with about 4 to 12V ac output for
powering the timer/display.

If you are into getting the last drop out of a salvage mission, then
you can usually get a moderate number of transistors and diodes off
the timer/display board.

The only problem I have found with doing the last thing on the list,
is you tear the microwave apart, then the last thing you do is go
after the timer board. When you get done pulling all the parts off of
it, and you test them to find out what they are. (NPN, PNP........)
you find one that is bad.......... Then it hits you........That
component ran the this and that....... That bad component is why the
microwave wasn't working....... Then you have to decide if it is
worth putting it all back together after you find out what
died........ I usually don't.

Good list we could add:
hardware (screws, washers etc)
mains power cord
some models have motorized wave "stirring" or magnetic drive platter turners
keypad for PIC projects

All in all, there's allot of good stuff in one. I shouldn't have thrown my
old one out.


Wow. Message received. It'll be fun to disassemble a microwave...when
I was a pre-teen, I used to do it to old 1st generation TV's the best
part used to be imploding the picture tube.

Thanks!

John
AB8O

The HV transformer. Output 1 to 2KV at several hundred to a thousand
KVA


Wow. Message received. It'll be fun to disassemble a microwave...when
I was a pre-teen, I used to do it to old 1st generation TV's the best
part used to be imploding the picture tube.

Thanks!

John
AB8O

Ow ow ow ow....... forgot to mention something........

Microwave oven transformers (MOTs) are current limiting. They have magnetic
shunts between the primary and secondary. You can short the secondary out,
and it won't blow any breakers. The transformer may hum loudly, but it but
nothing will blow.

That is why people say that they have poor voltage regulation when used in a
HV power supply.

You can remove the current limiting by just driving out the magnetic shuts
with a punch and hammer. The shunts are just stacks of transformer
laminations stacked up to make a square block, and press fit into the space
between the primary and secondary.

With the magnetic shunts removed, then the output voltage will go up, and
the output voltage regulation will be far better. You will be able to draw a
lot higher peak current from it. But be careful. There is no longer any
current limiting. If you short out the secondary, the breaker, or fuse will
blow.

jawod wrote:

I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this unit?

Thanks!

John
AB8O

It's definitely worth keeping the transformer if you have space to store it,
some people make spot-welders or arc welders from several microwave oven
transformers, by removing the secondary winding and winding on a new one.

I can't think of many sane uses for the intact magnetron but perhaps there
are some, given sufficient safety precautions.

I would strongly advise against applying power to the transformer with the
existing secondary winding in place, unless you can be *completely* certain
that you won't get a shock (e.g. all components and wiring should be inside
an earthed metal box). Those transformers will arc through clothing, will
provide more than enough current to kill you without blowing the fuse, and
the primary to secondary isolation means that earth-leakage circuit
breakers (also called residual current circuit breakers) will not protect
you. I certainly don't mean to discourage you from using the parts from
the oven but that is one appliance that really could kill you so just be
careful.

Chris

"Chris Jones" wrote in message
...
jawod wrote:

I have an old kitchen microwave unit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this
unit?

Thanks!

John
AB8O

It's definitely worth keeping the transformer if you have space to store
it,
some people make spot-welders or arc welders from several microwave oven
transformers, by removing the secondary winding and winding on a new one.

I can't think of many sane uses for the intact magnetron but perhaps there
are some, given sufficient safety precautions.

I would strongly advise against applying power to the transformer with the
existing secondary winding in place, unless you can be *completely*
certain
that you won't get a shock (e.g. all components and wiring should be
inside
an earthed metal box). Those transformers will arc through clothing, will
provide more than enough current to kill you without blowing the fuse, and
the primary to secondary isolation means that earth-leakage circuit
breakers (also called residual current circuit breakers) will not protect
you. I certainly don't mean to discourage you from using the parts from
the oven but that is one appliance that really could kill you so just be
careful.

Chris


Whenever I seea few at the GOODWILL I buy them for about $5 a piece.Most
work OKand
I have given several away to churches, GS and such. also put one in my
camper and built a power supply for my 4cx250 amp.

On Mar 14, 10:04 am, "N9WOS" wrote:
The HV transformer. Output 1 to 2KV at several hundred to a thousand
KVA

Wow. Message received. It'll be fun to disassemble a microwave...when
I was a pre-teen, I used to do it to old 1st generation TV's the best
part used to be imploding the picture tube.

Thanks!

John
AB8O

Ow ow ow ow....... forgot to mention something........

Microwave oven transformers (MOTs) are current limiting. They have magnetic
shunts between the primary and secondary. You can short the secondary out,
and it won't blow any breakers. The transformer may hum loudly, but it but
nothing will blow.

That is why people say that they have poor voltage regulation when used in a
HV power supply.

You can remove the current limiting by just driving out the magnetic shuts
with a punch and hammer. The shunts are just stacks of transformer
laminations stacked up to make a square block, and press fit into the space
between the primary and secondary.

With the magnetic shunts removed, then the output voltage will go up, and
the output voltage regulation will be far better. You will be able to draw a
lot higher peak current from it. But be careful. There is no longer any
current limiting. If you short out the secondary, the breaker, or fuse will
blow.

I never had much luck with Microwave power transformers. They seem to
saturate with light loads and draw several amps of line current. If
the load isn't 600 watts, they go crazy, draw lots of current and
heat up. They also have the laminations welded together which reduces
efficiency (lots of eddy currents). Might be better suited for a boat
anchor.

-Bill

On Mar 13, 8:21 pm, jawod wrote:
I have an old kitchenmicrowaveunit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this unit?

Ever consider getting it fixed?

Only $39.95 at http://www.microwavedisplay.com

I have an old kitchenmicrowaveunit whose only fault is that the
digital readout is broken. As a neophyte homebrew guy (kits only so
far...Elecraft K2, etc), Is there anything worth salvaging from this unit?

Ever consider getting it fixed?
Only $39.95 at http://www.microwavedisplay.com

Or, for that price or maybe $10 more, buy a NEW one!
(Yes, I know that's not "homebrew", but, after getting a new one,
you could then legitimately scrounge all the parts mentioned in
earlier posts from the old one.

Kids (and adults, too) just LOVE to play with 2-6 of those really-
strong cylindrical magnets strung NS SN NS SN... on a dowell!
Levitation is almost magic!

--
--Myron A. Calhoun; W0PBV
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
NRA Life Member & Certified Instructor for Rifle, Pistol, & Home Firearm Safety
Also Certified Instructor for the Kansas Concealed-Carry Handgun (CCH) license