Phil Allison wrote in message
...

"N_Kook"

Yes it would seem R-Core,

eg


http://www.dibao-transformer.com/Ima...ansformer-30VA.
png

I wonder how they are made.

** An R-core is wound with one continuous strip of steel - tapering at
each
end to get a round cross section. The two plastic bobbins are made as
halves
and glue together around each straight limb of the core.

There are also gear like teeth on the ends of the bobbins - allowing a
machine to spin them on the core while an operator feeds them with wire.

Then the bobbins and wire ends are secured and an overall insulation wrap
applied.

A steel claming frame is finally attached to allow chassis mounting.

Clever - huh ?


.... Phil







Ah! its now so obvious, had me scratching my head.
I never thought of winding the bobbins while on the core, yes clever.
I'd worked out how fully enclosed toroidal transformers with solid cores
were wound, a few months back, even made a sort of m/c for doing it, but
this type had me flumoxed

On a side matter relating perhaps to their efficiency.
The one in front of me gives off various voltages and the associated DCs are
marked on the overlay (no schematic available).
All the DC voltages , amplifier but just quiescent no load, all the actual
DC levels are about 10 percent less than the overlay marked DC. If one of
these C or R type cores is knocked/ abused / thermal stress/vibration and
the closure face opens up muicroscopically, could that cause a 10 percent
drop in secondary voltages?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/