GZPA 1.4000 DXII

[Achim1409]

I have changed now all Transistors on the drive board. The sine looks much better, but now the amp starts draw current, after increasing gain, and the good side of the fets heating up...

 

[Achim1409]

Mounted the other bank completely. Current draw in idle about 2.3 amps. Now it seems OK. I will put everything back in the heat sink and test for longer.

 

[Achim1409]

Reassembled everything, now it's the same again..
. I got crazy

 

[Achim1409]

As soon as I clamp this bank, it's distorted again. But I can't measure any contact between heatsink and middle pin.

 

[Bertje]

I didn't read the whole thread, but i measure with my Fluke scope with 10kHz lowpass filter in, when testing the class d mono's. Do you read a good sinewave then? I don't think there is a problem with the amp...?

 

[Achim1409]

No, there is no good signal, see the pics in the thread. I solved one problem, but now from one bank the high side fets get warm, and the upper sine wave is distorted again.

 

[Achim1409]

Just checked, high side signal is missing in one bank..

 

[Achim1409]

I have 12v across capacitor, but now ho... Low side is OK. So maybe the new driver is damaged

 

[Achim1409]

So, change the driver, signal everywhere good. Press the thumbs, I will reassemble it now.

 

[Achim1409]

So, still something wrong. Upper half same. After a few seconds, starts draw current. I have signal on high and low, but high on both sides looks different to low side.

 

[Achim1409]

High side with and without signal..

 

[Achim1409]

side with and without signal..can this be caused from the tl072? Audio signal is more distorted then before. If I give higher gain, above 10amps input, then it starts drawing more than 20amps,and don't go down, even when I remove input.

 

[Perry Babin]

#72:

Does this happen with only one side of the amp or does it do it no matter which side (alone) has FETs?

Are you sure that the output FETs that you're using are compatible?

Were all parts purchased from reputable distributors?

 

[Achim1409]

All parts are from Mouser. I dont know, if this are the orinigal fets. I contacted Ground Zero again, to give a diagram, or at least tell me the right fets.
I didnt tryed with one bank of.

But now im running out of ideas. I think its strange, that at very low power, everything is fine. If i increase output, so that the amp draws about 4-10 Amps, its starts disorting. After 10 Amps, but only sometimes, its starts draw eecesive current, so that my PS is limiting. Seems, that the high side is full open at this time, but still produce Audio...
Maybe the TVS are broken, or the signal diode on the drive board, iam not sure.


I think, it could also be the TL072, but then, i think, low and high side should be more disorted.

 

[Perry Babin]

How many terminals does the PS driver board have?

 

[Achim1409]

Here is a picture

 

[Perry Babin]

That's audio.

 

[Achim1409]

sorry, heres the right one.

 

[Achim1409]

So, removed the buffer stage, side by side. One side has more distortion on the upper sine wave, the other side much less. Still waiting for reply from ground zero...

 

[Achim1409]

Checked tl072 with buffer stage removed at max and medium gain at pin 2.seems to be OK. But at higher resolution.. I don't know