On Dec 19, 6:04*am, "N_Cook" wrote:
Well I only see it in USA kit. A toroid but flattened into an elipse shape
in plan view and a coil around each straight section. The curved ends of the
ring are exposed. Laminated core construction so easy coil winding ?

Not sure if you are referring to a 'flat pack' or a 'C' core
transformer. The Flat pack has squared 'U' shaped laminations, so if
you look at the core the lams are stacked [like in the common 'EI'
tranformer with the coil on the centre leg], but the two coils are on
the legs of the'U'.
The C core is more like what you describe with the core curved around
at each end and is made by winding the lamination strip around a
rectangular form, then compressing it on each long side to bond the
lam together, then cutting it in half midway along the 'long' side and
polishing the cut ends. Two coils are wound in the conventional manner
then the core halves slipped in and clamped [we used to use steel band
wrapped around the perifery of the core]. The ends could be epoxied
together, but that introduced a tiny air gap that affects the core
performance. This core design came, originally, from Germany IIRC. I
believe that the ones we were using back in the '60s came from Vacuum-
Schmeltz [sp?]

Neil S.