Hello all,

Last weeks I spend a lot of time rewindg transformers,
changing the circuit time after time, and even changing the FET's.

All in all I have little progess sofar..............

Maybe there is an error in the schematic, from which I do not know.

The output transformer and some of the surrounding components seem
to play a key role in the results obtained.

I tried the tip Jim, M0BMU gave, with 2x4t bifilair (made of 3x4x0.3mm wire)
as primaire coil, and 16 turns secundair.
This coil didn't gave the results I expected.
I found an primairy inductance of 150uH , between the two outher wires and
37uH between the centre tap and each outher wire.
The secundairry inductance around 600uH.

The best results I obtained with an 36mm green 3E1 core.
Primairy 2 times 8 turns bifilair, inductance 900uH
Secundairy wound on top of it 15 turns, inductance 814uH.
(I don't think this core can withstand 400Watt...... Ui=4000 about
twice as much as from a 3C90 core)

It seems that an almost 1:1 transformer gives the best results.

When measuring/compairing both transformers with an impedance bridge/noise
source
I found in both cases a strong 50Ohm dip in the 8-11MHz region, however
the M0BMU transformer wound on an ex-monitor core gave also another
dip of about 500Ohm around 1400kHz.

I am testing with a variable supply voltage to the FET's, and I think for
50V/10A
I should find somewhere around 4A at 20V.........

Maybe somebody has something to say about this......

73 Dick, pa4vhf