DD Z1a damaged

[Perry Babin]

Now you can remove the Q10 jumper and see if the amp will produce low power audio.

 

[Achim1409]

It produces audio. If i remove the rca, i still have hissing noise. Maybe from my battery charger. Do you think that was all, or should i increase the voltage to test more.

 

[Perry Babin]

Increasing the voltage incrementally is the safest method.

If the problem was excessive current draw, I don't think the op-amp was causing it.

Note whether the frequency increases as the voltage increases (if you test that way).

 

[Achim1409]

The Frequency increase every more winding. I have now about 21khz.
Picture above is Highside

 

[Achim1409]

at 30V i have 27khz, but i cant trigger it good, because its moving on the timebase a little, but very quick. Is that normal?

 

[Perry Babin]

If you have audio driving it, it's normal. If you have noise coming from the preamp circuit, that could also be causing it.

 

[Achim1409]

i have no audio connected. Working only on battery but still high frequency hissing noise is comming out of the speaker.
With 40V the lamp start lit.

 

[Perry Babin]

See if one group of parts is starting to heat more than others.

Disconnect the preamp board too see if the noise goes away.

 

[Achim1409]

without pre amp the noise is still there, but its only high frequence noise and more stable. One Bank of fets with highs and lows getting more hot.

 

[Perry Babin]

Do the waveforms in the gates of those FETs look different than the others?

I think you said you tried it but try pushing/pulling/twisting the inductor for that group.

 

[Achim1409]

yes, i tried, but nothing happen. Waveform is everywhere the same. Sound starts intermittend after a few seconds. Like peep peep peep, but very short impulses.

 

[Perry Babin]

Is audio constant from the preamp section (pin 14)?

Is the amp going, repeatedly into protection?

Are all of the FETs for that group heating at the same rate?

Would it be easy to desolder one leg of the inductor for that section?

Isn't it like 4 in the morning in Germany?

 

[Achim1409]

No, its 7PM. Preamp board is dismounted all the time. It seems that they heat all same. From another group it looks, that only high side is heating. The inductors doesnt heat up, but i can desolder them. No Protection at all.

 

[Perry Babin]

The only reason to desolder the inductor was to see if it was loading the outputs for that group.

Can you rephrase:
It seems that they heat all same. From another group it looks, that only high side is heating

 

[Achim1409]

I rechecked. All Fets getting hot. From every group.

 

[Achim1409]

Is it possible because of cheap China fets? Or maybe The deadtime isnt correct?

 

[Perry Babin]

I generally ask up front about the FET source. I can't believe that I didn't here. YES.

 

[Achim1409]

Ok, i will order good one.

 

[Achim1409]

I removed the chinese parts and left only a few from the quality parts. After switching on, it draws a lot of amps, because the bulbs lit very strong. In that same moment the speaker made noise again and some smoke came from the drive board. So will order parts again.

 

[Achim1409]

Only for my understanding, how that Amp produce audio.
Low side makes negativ voltage and high side positive voltage. If both sides in balance there is no audio. If they are unbalanced IT produce audio. That means, that the noise what i had is from unbalance from both sides.
Is that correct?