Hi Bill & ball,
Thanks for the info on the stuff I'm seeing in your photos. I think
it's good to see how others solve problems. I think you will do fine
with one emitter for the size of bell jar you have. If not you can
add more later.
Cutting the secondary winding off a MOT is very easy. Get a sharp
wood chisle and a small mallet or hammer. Start by chopping off the
outer edge of the windings and then work towards the core. A sharp
steel wood chisle cuts through the thin copper wire windings like
butter. When you get the exposed end of the coil cut flush with the
core take a piece of wood or metal and use it to punch the rest of
the coil out of the core with a hammer.
Make sure you are cutting off the correct coil. The one with the
thin wire is the secondary that we don't need. There may be another
winding of just a few turns in with the secondary winding. This is a
filament winding for the magnetron. We do not need that winding. The
primary will have heavier windings and be careful so you do not
damage the primary. Just take your time. It helps if you can put
the transformer in a vice and position it so it's easy to work on.
There will be sections of laminated steel between the primary and
secondary windings. These are shunts and are needed so do not remove
these either. I'm going to try some clear Poly Tape I got from Ace
Hardware to insulate the copper strips. Two layers should do it.
I got the idea to use the flat copper strips for secondary windings
from
he indicates they work well. Here is the write-up from his files
section:
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
REWINDING MOT'S FOR LOW VOLTAGE
FOR HIGH CURRENT PROJECTS-BATTERY CHARGERS-FILAMENT HEATERS-
ELECTROPLATING-SPOT WELDERS-
ECT.
To rewind an old microwave transformer make sure the primary winding
is good and not damaged
during rewinding now saw off
one side of the secondary the smaller wire I used a bandsaw and
press or drive it
out with a drift or wooden dowel. Take out the mica hv insulation for
more room for the new winding. The mot in the photo has 1 3/8 inch
slot I used 1 ? by .025 copper 8 feet long that gave 9 turns with 2
layers of clear shipping tape [mylar] for insulation .
You will get 1.06 volt per turn the larger the wire the higher the
current this winding will give 145 amp
And 9.61 volt under no load With out to much heating with 20 amp
input at 120 volt ac. Under full load
Will give 8 volt and a full wave bridge rectifier will drop the
voltage another 1.7 volt 6.3 volt final output.
A cheap light dimmer will not controll this the induction feed back
will burnout the triac but if you have a microwave that the
transformer came from it has a 45 amp triac in it that controls the
mot for the magnatron that can repace the one in a cheap dimmer Ihave
made several of these I use one on my electric metal melting
furnace.I used copper flat metal because heavy wire is very hard to
wind around the core you can saw or gring the weld on the core remove
the primary and secondary but they are hard to replace and have to be
tig welded back, also aluminum will work almost as well like the kind
used for trim work on vinyl on metal siding, I do siding and most of
those guy have narrow strips left from where they cut trim for the
facia and window areas and will be happy to give you some. I get my
copper from the metal salvage yard they have a ben in side with
copper scrap it is about $1.45 pound 1 pound will do a mot.
By ed ward edsworkshp
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Good Luck!!
Roy
--- In VacuumX@..., William Belisle
<williambelisle2003@...> wrote:
Hi Roy,
The metal contraptions are there simply to support some test pieces
of glass to see how well they would be aluminized. They're not
mounted to the base plate - just sitting on it. And no, they aren't
insulated (for high voltage) nor are they glow bars. Those will come
later (with any luck). The smaller metal disks you see in the photos
are just stainless blanks to close holes in the baseplate.
How did you cut the high-voltage winding from your MOT? I'm at the
point where I have the transformer ready to cut off the HV winding,
but am not sure how to proceed. I read that some people are using a
hammer and chisel but your cut looks so clean; Dremel? Sawzall? Band
saw? Any suggestions?
Also, do you think the copper flashing will be better than heavy-
gauge wire for the secondary winding? And how do you plan to insulate
it? I plan on using only a single filament for evaporating aluminum
(mistake?) so maybe I don't need that much power. Your thoughts
always appreciated!
Bill
--- On Mon, 9/29/08, radroy92 <rminnich@...> wrote:
From: radroy92 <rminnich@...>
Subject: [VacuumX] Bills vacuum system
To: VacuumX@...
Date: Monday, September 29, 2008, 2:16 PM
Hey Bill,
What are those metal bars that mount on the base plate? Some sort
of
support for something to be metalized? Or glow bars? They don't
look
insulated for HV coming out of those big metal hockey pucks.
Also I found another smaller (800 Watts) microwave oven. I have
the
transformer prepared for the new secondary winding. I have some
copper
flashing I cut into strips to use for the secondary winding.
Roy M.
