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.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek