Korean half bridge amp strange issue

[Achim1409]

I have this 2k zenon amp here. It seems, it works fine..i have on each mosfets audio and ps a good signal. The amp needs about 7 amps to start,
then it idle at 3.3 amps.. If I use a power supply with only 5 amps, it won't power up fully, but all signals are there. Voltage drops at my bench supply to 7v..

With a bigger supply no problem. If I use a resistive load 4 ohm and inject 50hz,also everything looks fine. If I increase to clipping, or better to the fully 30amps from my bench supply,
The rail voltage breaks massive down. Even if I just touch the limit of my bench supply, the rail drops more then the half of voltage.. What could cause this?

 

[Achim1409]

Here are some pictures.. It's a slightly move on the gain, the current increase just to the limit of the supply, than the rail drops.

 

[Perry Babin]

How low is the 12v supply dropping when the rail voltage collapses?

Confirm that you have a good drive signal on every output FET They are driven by 8 driver groups and the amp will seem to function normally even if several of the driver groups are dead/weak.

 

[Achim1409]

The voltage drops from 14.4 to 10v..i checked each output mosfet, signal is there. I checked on each output inductor..
Signal is good. If I go beyond the limits of my supply, it seems that the amplitude of the output is gone..
The measure is taken from one output inductor, input voltage down to 10v.

 

[Perry Babin]

How do you test large amps without a larger power supply?

 

[Achim1409]

At work I have only this small supply. At home I have a 160amps supply.

 

[Perry Babin]

I think I'd try it on the larger supply before I'd waste too much time on troubleshooting.