it oscillates. the amplitude is moving from left to right and back always a little bit. I have tried with 100Hz, but it seems nothing. I was expecting that the voltage was to low.
Was it oscillating at a high frequency (80kHz) when you were driving the 100hz signal into it?
Did you try connecting a speaker and listening to it?
Did you try connecting a speaker and listening to it?
I didnt checked. Allready i took the board out of the heatsink. I will remove the rectifiers again and start with low voltage again.
If you think it's a voltage related issue, you can increase the voltage incrementally by increasing the turns a little at a time. Wind the initial turns but leave a long length of wire at the end of the winding. Then desolder that wire and make another turn or two and reconnect the wire.
on the drain low side i have same signal. On the high side there is only dc, but on high side source i have signal.
Follow the signal path back. It likely goes to a 10uf cap. Find the op-amp driving that cap and check the signal there.
Secondary ground. You can use the audio ground next to the input on the driver board if you can do so without slipping and shorting between pins.
