GAS PSP2500.2DF. (made by A/D/S)

[yoppi]

Hi.
I'm working on this GAS PSP2500.2DF amplifier (made by A/D/S, model APA21700DFB. http://www.adsaudio.cc/webs/carAudio/detail?id=1000111 )
The amplifier always turns on in protection mode.
On first start, a PWM pulse is given in the power supply, which charges the rail capacitors to +/- 50VDC. If you disconnect the remote and reconnect it, the PWM pulse in the power supply does not appear until the rails are discharged. I have checked both channels and they are correct, I have even replaced the 2092 ICs. I have also checked the power supply control board and everything seems to be in order.
Has anyone had a similar problem?I hope I have explained myself well.

Thanks.

 

[yoppi]

I have also managed to turn it on without the rectifier diodes on the rails, all the auxiliary voltages are present (+/-5v +/-15v +12v)

 

[Perry Babin]

If you drain the rail caps, does it produce rail and audio every time you power up?

 

[yoppi]

Hi Perry.

does nothing, remains in protection.

 

[Perry Babin]

When it powers up, does it ever produce audio?

 

[yoppi]

No, it doesn't produce audio or any "pop". Nothing.

 

[Perry Babin]

With the rectifiers in the circuit, does it produce rail voltage or pop the speakers?

 

[yoppi]

Without rectifier diodes it also doesn't produce any noise or "pop". The only way to make it sound has been by removing the rectifier diodes and connecting remote. This way it turns on without protection, then I injected +/-20V into the rails from an external power supply (2 laboratory power supply in series). This is the only way it sounds normal. If I first inject +/-20V into the rail and turn on remote, it goes back to protection, the same way as with the rectifier diodes installed on the board.
This is all a bit strange, I hope you can understand me.

 

[Perry Babin]

What is the difference in voltage on pins 1 and 7 on the 8-pin IC on the PS driver board with and without rail voltage (in and out of protect)?

 

[yoppi]

I found the problem. A tiny, almost microscopic copper wire touching the + rail with the tap of the output coil of a channel.
Thanks for your help Perry