| Author |
Message |
Engineer
Guest
|
 Posted:
Sun Oct 23, 2005 3:45 am Post subject:
OT: Transformer from a microwave oven |
|
|
Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts between the windings to give, I think, a degree of
voltage regulation (I may be able to press or knock them out, but I've
not tried yet.) The 120 volt primary resistance is about 0.3 ohm; the
2 KV secondary is 115 ohms.
Can anyone think of something useful to do with this this transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer (but
watch the 2 KV floating around!)
2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8
ohm speakers - too low; also need to isolate the secondary from the
frame (easy enough to do).)
3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety engineering
required.) Much too big, though.
4. Run it off a suitable battery and interrupter (NOT AC mains!) to
power an electric fence.
5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
6. Use to replace another failed one <g> Do they ever fail?
That's it. Thanks for all ideas.
Cheers,
Roger
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David Brooks
Guest
|
| Posted:
Sun Oct 23, 2005 4:14 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
Collect a few more (heck, they're free!).
Rip off the secondaries (can sleep easy, now :), stack them together, &
run several plies of copper tape through them in series, to get a
single-turn secondary of about 2V at 2000A.
Voila: spot welder!
Engineer wrote:
| Quote: | Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts between the windings to give, I think, a degree of
voltage regulation (I may be able to press or knock them out, but I've
not tried yet.) The 120 volt primary resistance is about 0.3 ohm; the
2 KV secondary is 115 ohms.
Can anyone think of something useful to do with this this transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer (but
watch the 2 KV floating around!)
2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8
ohm speakers - too low; also need to isolate the secondary from the
frame (easy enough to do).)
3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety engineering
required.) Much too big, though.
4. Run it off a suitable battery and interrupter (NOT AC mains!) to
power an electric fence.
5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
6. Use to replace another failed one <g> Do they ever fail?
That's it. Thanks for all ideas.
Cheers,
Roger
|
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Phil Allison
Guest
|
| Posted:
Sun Oct 23, 2005 4:29 am Post subject:
Re: Transformer from a microwave oven |
|
|
"Engineer"
| Quote: |
Can anyone think of something useful to do with this this transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer (but
watch the 2 KV floating around!)
|
** = will get very hot and have *terrible* voltage regulation.
| Quote: | 2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8
ohm speakers - too low; also need to isolate the secondary from the
frame (easy enough to do).)
|
** = no high frequency or low frequency response.
Microwave oven trannys have very high leakage reactance and cannot stand DC
in the secondary.
| Quote: | 3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety engineering
required.) Much too big, though.
|
** You said it.
| Quote: | 4. Run it off a suitable battery and interrupter (NOT AC mains!) to
power an electric fence.
|
** Every home needs one of them to keep the neighbour's kids out.
| Quote: | 5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
|
** No air gap so unsuitable for DC operation.
| Quote: | 6. Use to replace another failed one <g> Do they ever fail?
|
** Use it for bloody door stopper.
............ Phil |
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Bret Ludwig
Guest
|
| Posted:
Sun Oct 23, 2005 4:42 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
John Stewart wrote:
| Quote: | Engineer wrote:
Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts
The magnetic shunts render the transformer a current source, something
required by the magnetron. So the voltage regulation will be poor,as it is
intended.
Cheers, John Stewart
|
You could dismantle it, remove the shunts, and salvage its wire
(copper scrap if you can burn it off) and lams.
There's a guy in Australia that does a lot with these things, but my
opinion is if you want to wind transformers, buy new lams. Fifty bucks
is a lifetime supply. |
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| Back to top |
|
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Patrick Turner
Guest
|
| Posted:
Sun Oct 23, 2005 4:42 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
Engineer wrote:
| Quote: | Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts between the windings to give, I think, a degree of
voltage regulation (I may be able to press or knock them out, but I've
not tried yet.) The 120 volt primary resistance is about 0.3 ohm; the
2 KV secondary is 115 ohms.
Can anyone think of something useful to do with this this transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer (but
watch the 2 KV floating around!)
2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8
ohm speakers - too low; also need to isolate the secondary from the
frame (easy enough to do).)
3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety engineering
required.) Much too big, though.
4. Run it off a suitable battery and interrupter (NOT AC mains!) to
power an electric fence.
5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
6. Use to replace another failed one <g> Do they ever fail?
That's it. Thanks for all ideas.
Cheers,
Roger
|
After many years scrounging for parts for experimental circuits,
I found no useful purpose for microwave trannies.
Patrick Turner. |
|
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|
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John Stewart
Guest
|
| Posted:
Sun Oct 23, 2005 4:42 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
Engineer wrote:
| Quote: | Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts
|
The magnetic shunts render the transformer a current source, something
required by the magnetron. So the voltage regulation will be poor,as it is
intended.
Cheers, John Stewart
| Quote: | between the windings to give, I think, a degree of
voltage regulation (I may be able to press or knock them out, but I've
not tried yet.) The 120 volt primary resistance is about 0.3 ohm; the
2 KV secondary is 115 ohms.
Can anyone think of something useful to do with this this transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer (but
watch the 2 KV floating around!)
2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget about 8
ohm speakers - too low; also need to isolate the secondary from the
frame (easy enough to do).)
3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety engineering
required.) Much too big, though.
4. Run it off a suitable battery and interrupter (NOT AC mains!) to
power an electric fence.
5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
6. Use to replace another failed one <g> Do they ever fail?
That's it. Thanks for all ideas.
Cheers,
Roger |
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|
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flipper
Guest
|
| Posted:
Sun Oct 23, 2005 12:24 pm Post subject:
Re: OT: Transformer from a microwave oven |
|
|
On 22 Oct 2005 19:35:26 -0700, "Bret Ludwig" <bretldwig@yahoo.com>
wrote:
| Quote: |
John Stewart wrote:
Engineer wrote:
Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs, and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts
The magnetic shunts render the transformer a current source, something
required by the magnetron. So the voltage regulation will be poor,as it is
intended.
Cheers, John Stewart
You could dismantle it, remove the shunts, and salvage its wire
(copper scrap if you can burn it off) and lams.
There's a guy in Australia that does a lot with these things, but my
opinion is if you want to wind transformers, buy new lams. Fifty bucks
is a lifetime supply.
|
Where does one buy them? |
|
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|
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Bret Ludwig
Guest
|
| Posted:
Mon Oct 24, 2005 12:17 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
Where one buys most OEM products, the manufacturers. Look in the
normal places, maybe Thomas Register or EEM, under "transformer
materials" or "electrical steel" or "magnetic materials" and get some
manufacturer names, so you can search their web sites. They also have
catalogs and data sheets you can send off for.
Good books on transformer winding exist and will have manufacturer
names and addresses in the appendices as well.
I am not providing the manufacturer names here, as the search is half
the fun and necessary exercise. |
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|
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Engineer
Guest
|
| Posted:
Mon Oct 24, 2005 3:32 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
"Bret Ludwig" <bretldwig@yahoo.com> wrote in message
news:1130034926.033189.150480@o13g2000cwo.googlegroups.com...
| Quote: |
John Stewart wrote:
Engineer wrote:
Hi, vacuumlanders.
|
(snip)
| Quote: | I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs,
and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has
two
magnetic shunts
The magnetic shunts render the transformer a current source,
something
required by the magnetron. So the voltage regulation will be
poor,as it is
intended.
Cheers, John Stewart
|
He's dead right, of course. Tks, John.
| Quote: |
You could dismantle it, remove the shunts, and salvage its wire
(copper scrap if you can burn it off) and lams.
|
I fear not. The whole thing is cost-engineered to the nth degree. The
lams are seam welded in several places - no bolts - and the whole core
block is massively spot welded to the base plate - 4 spot welds, each
nearly 1/2 inch across with close to as big a dent as a 0.308 hitting
tractor iron!
This is one ugly transformer with virtually no civilised re-use. <g>
Cheers,
Roger
(snip) |
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flipper
Guest
|
| Posted:
Mon Oct 24, 2005 4:43 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
On 23 Oct 2005 12:17:12 -0700, "Bret Ludwig" <bretldwig@yahoo.com>
wrote:
| Quote: | Where one buys most OEM products, the manufacturers.
|
More often a distributor as many manufacturers will not sell to
individuals.
| Quote: | Look in the
normal places, maybe Thomas Register or EEM, under "transformer
materials" or "electrical steel" or "magnetic materials" and get some
manufacturer names, so you can search their web sites. They also have
catalogs and data sheets you can send off for.
Good books on transformer winding exist and will have manufacturer
names and addresses in the appendices as well.
I am not providing the manufacturer names here, as the search is half
the fun and necessary exercise.
|
You and I have different opinions on what constitutes 'fun' and the
amount of searching I've already done far exceeded it long ago. |
|
| Back to top |
|
|
Bret Ludwig
Guest
|
| Posted:
Mon Oct 24, 2005 4:43 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
flipper wrote:
| Quote: | On 23 Oct 2005 12:17:12 -0700, "Bret Ludwig" <bretldwig@yahoo.com
wrote:
Where one buys most OEM products, the manufacturers.
More often a distributor as many manufacturers will not sell to
individuals.
In which instance they will refer you to one. Or give you samples if |
it's less trouble.
| Quote: | You and I have different opinions on what constitutes 'fun' and the
amount of searching I've already done far exceeded it long ago.
|
You weren't very effective at it. I bet I could find 20 mag materials
places on the net in as many minutes. |
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|
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Bret Ludwig
Guest
|
| Posted:
Mon Oct 24, 2005 4:43 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
flipper wrote:
| Quote: | On 23 Oct 2005 19:15:01 -0700, "Bret Ludwig" <bretldwig@yahoo.com
wrote:
snip |
| Quote: | I can find lots of 'mag materials' places too but what I'm interested
in is a place selling iams and I just thought, since you were tossing
out 'lifetime supply' costs, you might have some idea where to get
them but don't worry about it. It's not worth 'the game'.
|
Lams are magnetic materials. Thomas Register or eem.com are the first
internet places to look.
If you live in any sizable city, there will be some transformer
winders in town. They will probably GIVE you a handful of lams or a
miswound or failed new one you can dismantle. Certainly they will give
you manufacturer names and probably those of the reps they deal with
who might give you a spare, off case of them.
I haven't bought any in probably 20 years. Any names I gave you even
if I could remember would probably be obsolete-corporate acquisitions
and what not. |
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|
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flipper
Guest
|
| Posted:
Mon Oct 24, 2005 4:43 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
On 23 Oct 2005 19:15:01 -0700, "Bret Ludwig" <bretldwig@yahoo.com>
wrote:
| Quote: |
flipper wrote:
On 23 Oct 2005 12:17:12 -0700, "Bret Ludwig" <bretldwig@yahoo.com
wrote:
Where one buys most OEM products, the manufacturers.
More often a distributor as many manufacturers will not sell to
individuals.
In which instance they will refer you to one. Or give you samples if
it's less trouble.
|
Sure. I was just commenting on "Where one buys most OEM products."
| Quote: | You and I have different opinions on what constitutes 'fun' and the
amount of searching I've already done far exceeded it long ago.
You weren't very effective at it.
|
You have no idea and I was referring to 'searching' in general as
'fun'. I've searched for lots of things and it is no longer 'fun' or
even half of it as I am more interested in finding what I'm looking
for and not in playing hide and seek.
| Quote: | I bet I could find 20 mag materials
places on the net in as many minutes.
|
I can find lots of 'mag materials' places too but what I'm interested
in is a place selling iams and I just thought, since you were tossing
out 'lifetime supply' costs, you might have some idea where to get
them but don't worry about it. It's not worth 'the game'. |
|
| Back to top |
|
|
Ian Iveson
Guest
|
| Posted:
Tue Oct 25, 2005 2:43 am Post subject:
Re: Transformer from a microwave oven |
|
|
DIY radar?
Ian
"Engineer" <fakeaddress@nowhere.net> wrote in message
news:RpKdnQUjD7NgXcfenZ2dnUVZ_smdnZ2d@rogers.com...
| Quote: | Hi, vacuumlanders.
I posted this to the NG "sci.electronics.design" but I think this
group may well have some good ideas, so here it is....
This may seem an odd post but I'm an avid re-user and recycler of
old
and/or scrapped electronic stuff (especially tube equipment), so I
hope all will be clear...
I have just picked over the carcass of a dead microwave oven (free
junk from a church sale) to get a thermal switch to repair our
main
unit, but that's another story...
I pulled out all the usable bits (not many!) but also the power
transformer. It has a 1.75 x 1,25 inch core, weighs 9 1/4 lbs,
and is
120 VAC to a scary 1,925 VAC (measured off load.) The core has two
magnetic shunts between the windings to give, I think, a degree of
voltage regulation (I may be able to press or knock them out, but
I've
not tried yet.) The 120 volt primary resistance is about 0.3 ohm;
the
2 KV secondary is 115 ohms.
Can anyone think of something useful to do with this this
transformer.
All I can come up with is:
1. Use two of them back to back as a bench isolation transformer
(but
watch the 2 KV floating around!)
2. Use as the OPT for a weird single-ended tube amplifier with 3.8
Kohm plate impedance (rather low) to a 15 ohm speaker (forget
about 8
ohm speakers - too low; also need to isolate the secondary from
the
frame (easy enough to do).)
3. Use it with a voltage doubler or tripler for an electrostatic
filter (would not fit inside most units so serious safety
engineering
required.) Much too big, though.
4. Run it off a suitable battery and interrupter (NOT AC mains!)
to
power an electric fence.
5. Use it as a choke in a tube power supply. I'm not sure of the
secondary winding inductance or current rating. Again, isolate the
secondary.
6. Use to replace another failed one <g> Do they ever fail?
That's it. Thanks for all ideas.
Cheers,
Roger
|
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| Back to top |
|
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Engineer
Guest
|
| Posted:
Thu Oct 27, 2005 4:42 am Post subject:
Re: OT: Transformer from a microwave oven |
|
|
"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:435B01B4.B1A50DE8@turneraudio.com.au...
| Quote: |
Engineer wrote:
Hi, vacuumlanders.
|
(snip)
| Quote: | Can anyone think of something useful to do with this this
transformer.
All I can come up with is:
|
(snip)
| Quote: | After many years scrounging for parts for experimental circuits,
I found no useful purpose for microwave trannies.
Patrick Turner.
|
I've come to the conclusion that you are quite right! They don't
even have a usable primary since the magnetising current is far too
high at about 3 amps (120 VAC in and shunts removed.) I'd say it has
about a 30 VAC primary for about 2 1/2 turns per volt, hence a 500 VAC
secondary..
And too ugly even for an "object d'art"!
Cheers,
Roger |
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