BAMF 2200.2

[Hexhclass]

Amp has no output. Rail voltage is present and regulated voltage for op- amps is also there.I get audio reaching the driver boards. Original problem was bad output drivers for one channel.I don't know if it has a mute circuit. Any ideas?

 

[Perry Babin]

Post the DC voltage on all pins of one of the audio driver boards (confirm that the voltages are essentially the same for both boards) and note which pin has audio.

 

[Hexhclass]

Voltages look the same.I see audio on pin 9 of both boards

1:39.04
2:-0.142
3:-0.015
4:0.001
5:0.014
6:0.001
7:-0.124
8:0.023
9:-0.022
10:0.106
11:-39.05

 

[Perry Babin]

I think you should have ±regulated voltage on the second pin from each end. From the photos I have of the 4ch version, it appears that those pins connect to the 8-pin op-amp behind the driver boards (IL4558, U502 in the amp I'm using as a reference). Pull that op-amp. Does that allow the two pins to get ±regulated voltage?

Be careful. Watch for any problems. I'm not sure how they're using that op-amp. It could be part of a protection circuit and removing it could prevent the amp from protecting itself.

 

[Hexhclass]

yes these pin do connect to that op-amp.When i pull the op-amp it put the amp in protect mode.pin 4 on the pwm IC goes to 4.76v

 

[Perry Babin]

When you power the amp up, do you see an instantaneous pulse of DC on either channel?

You need to check either on the emitter resistors or on the bridging speaker terminals.

 

[Hexhclass]

Found it
Pin 3 of that same op-amp is connected a a transistor all the way in the PS section Q2.
I replace it and now have Reg 9v on the driver board. It now has output.

thanks