"Ronald" wrote:

: Thanks !!
:
: I'll take a look ....

You're welcome

: Quote from your mail :
: Wish I had copied the actual circuit section - but I doubted that I'd ever
: find
: 800ohm speakers, and it still seems unlikely;-)
:
: It's not that hard to put a tranny in . It can be a normal PSU tranny since
: there's
: no DC current . A 220V pri. - 22V sec. will work for an 8 ohms speaker .

I suppose that's a point, although I doubt much useful HF from such.
I've saved a 26V (and 28V, too) xfmr, but for the purpose of a filament
transformer for a quad of 6159B, (26.5Vfil 6146) when I get around to it!

: Might do nicely for multy-media .......

Like freq-resp limited rear channels, as in Dolby Pro-Logic or simpler:-?)

: 800 ohms speakers are very common in old Philips tube-radio's over here in
: NL .

I've never seen any here, although not to say none came out ...
I do have a pair of "full range" 12" AD1256-M8 drive units though. In other
discussions I've been told their bass is not so great compared to 1256W.
My Philips speaker book doesn't cover them, although it has the 1256W.
I guess the "M" essentially means "midrange", but they might be fun ...

But back to the subject - how do you reckon these chokes are constructed?
The diagram shows them looking like a 1:1 transformer - in a sense it is.

"As the direct currents flow through the windings of the choke in opposite
directions, the magnetic fields neutralise each other and the core is thus not
magnetised; there is thus no need for an air-gap, resulting in a component
which is small but which nevertheless has a high inductance."

This shouldn't be too hard to make - and the screen currents are not high.