There was an article in QEX written by WI5W about this subject.
I once found this article on the internet, but could'nt find the page
again. Here the info abt the article :

Randy Henderson, WI5W,"Build a High-Voltage Power Supply at Low Cost"
QEX, Jan/Feb 1998 Pg. 47-51.

Hope this helps !?

73, greetings from Corsica. TK5EP

http://tk5ep.free.fr


Dan/W4NTI a écrit :
Does anyone know what kind of AC voltage a Microwave oven transformer would
put out? Are they center taped or just a single coil?

I need a replacement for my homebrew 3-500z single tube amp. I only used it
for low power AM and I don't need "maximum voltage".

Dan/W4NTI

On Tue, 5 Apr 2005 08:23:02 +0100, Ian White G3SEK
wrote:

Michael A. Terrell wrote:


The welded cores can cause problems. This has been discussed on the
various sci.electronics.* groups a number of times

The key phrase to search for is "magnetic shunt". Typically the magnetic
shunt consists of two extra blocks of laminations between the primary
and secondary bobbins. This has been added to give the transformer a
current-limiting characteristic, which is necessary to power a magnetron
- but is exactly the opposite of what you need for normal vacuum tubes.

In many oven transformers, the magnetic shunt blocks can be driven out
with a large punch, to leave a more normal-looking transformer.

The not-so-good news is that you're still left with a transformer that
has a very high secondary voltage and rather high secondary resistance,
which will give poor voltage regulation in typical amateur use. Also one
end of the secondary winding is usually grounded to the core. Even if
you can get to the grounded end to disconnect it, the insulation close
to the core is not designed for typical full-wave bridge applications.

Some people have had limited success with a pair of identical
transformers connected as a "centre-tapped" winding... but remember that
in two separate transformers the core magnetization by the DC components
will not cancel.

It all seems like a lot of effort for rather poor results.

The worst problem is idle current, 1.2-1.5A on 240VAC, so you should
use the extra space and add 100turns for the primary, and reduce the
idle current to 0.3A. This will also reduce the output voltage below
2kV DC. Many cores are standard E120 types and it isn't worth the
trouble of trying to use the original rubbish

I've planned to bring some information on
http://home.online.no/~la8ak/d4.htm , but haven't translated it into
English yet

73
LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm