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.

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

"Bill Bowden" wrote in message
ups.com...
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


I tried one for a 4cx250 amp, sucked bilge water big time. I dont think the
primary had 100 turns on it.

Jimmie