Rockford Fosgate BD1000, green led & protect led lit.

[djmdp]

Hello, sorry for my poor english, I finally bought myself this powerful amplifier with some kind of issue. Green and red leds both lit. Power supply is working ok I guess (there's 115V beetween H+ and H- cable) and there's no shorted FETS or diodes. Everything's look fine, even D Class FETS. I have measured voltages of U21 OPamp, there it is:
Pins:
1 -> -8.31V
2 -> 0V
3 -> -8.84V
4 -> -9.67V
5 -> 5V
6 -> -6.2V
7 -> 8.47V
8 -> 9.81V
I read some posts and replies (includes Perry Babin's), but I have no clue why is it in protection mode. I can do more measures.
It's the BD1000a1 model.

 

[Perry Babin]

U21 is defective.

 

[djmdp]

Btw, can I ask You about schematic for this amp (djmdp@o2.pl)? It's the half bridge topology, so there supposed to be symmetrical rails. When I'am measuring H+ and H- (to ground) there's no H- Voltage (0V). I would replace this IC.

 

[Perry Babin]

The rails float in these amps. When the amp is in protect, the rails are completely isolated from the rest of the circuit which means that you will read 0v if you use the primary ground as the reference.

 

[djmdp]

Hehe when I saw this circuit just understood that, thanks for diagram Perry, I'm ordering OPamp.

 

[djmdp]

I replaced this U21 OPamp and amp powering up well, there's no Protect led after 2secs from start. I haven't got any speaker yet, so we must wait till weekend with tests.