DD Z1a damaged

[Perry Babin]

Are you saying that the lamp was always lit?

 

[Achim1409]

no, it doesnt lit.

 

[Perry Babin]

Did the amp oscillate and produce low power audio on low voltage?

 

[Achim1409]

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.

 

[Perry Babin]

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?

 

[Achim1409]

No, always 17khz.no i dont put a speaker

 

[Perry Babin]

What's the frequency of oscillation with high voltage?

 

[Achim1409]

I didnt checked. Allready i took the board out of the heatsink. I will remove the rectifiers again and start with low voltage again.

 

[Perry Babin]

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.

 

[Achim1409]

Both Pictures with low Voltage. 5 turns about 20v. 1st. Picture High Gate, 2nd Low Gate

 

[Achim1409]

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.

 

[Perry Babin]

That's normal.

Will the amp produce audio at low power?

 

[Achim1409]

only disorted noise with high frequencies

 

[Achim1409]

the same with disconnected pre-amp section

 

[Perry Babin]

Are you getting an audio signal to the driver board?

 

[Achim1409]

Only this signal. Very disorted. Measured on Pin 15 Audio in, ground probe on low side shunt

 

[Perry Babin]

Follow the signal path back. It likely goes to a 10uf cap. Find the op-amp driving that cap and check the signal there.

 

[Achim1409]

where should i connect my ground from the oscilloscope?

 

[Perry Babin]

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.

 

[Achim1409]

I took ground from the cinch insert ground.
At Resistor R168 i have that signal. After R168 the Signal drops more to negativ (Below center line). After that OP´s i have only DC