Vibe

[Hexhclass]

This amp is producing good audio but will go in protect if I try to turn up the gain or increase the input signal.It will protect when it reaches about half of its full power,

any suggestions?

 

[Perry Babin]

Does it go into protect at the same output level (voltage across the speaker terminals), regardless of the load?

Or does it go into protect at approximately the same current draw from the 12v supply?

 

[Hexhclass]

It goes in protect at the same output level with 2 ohms and 4 ohms load.

 

[Perry Babin]

Could it be due to low voltage from the 12v supply?

What are the driver ICs and the optocouplers(?) on the driver board?

Photo of the PS driver board?

 

[Hexhclass]

It was doing the same thing in the car with good electrical .

IC scratch out but I think it is using irs21844s

 

[Perry Babin]

Do you see pin 1 or pin 7 going high on the LM393 on the PS board when the amp goes into protect?

 

[Hexhclass]

Pin 1 an 7 does not go high.
Pin 3,4,9 on the 494 also not going high.So the PS not going in shutdown only the relay disengaging and the protect LED comes on.

 

[Perry Babin]

Was this amp working normally and then started doing this?

Post the DC voltage on all terminals of U6 on the audio driver board (black probe on the negative rail). Copy and paste the following list and fill in the blanks.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

 

[Hexhclass]

I got the amp in that condition.It looks like it has been repaired in the past but i am not sure if it was working properly after that repair.
Owner bought it used with that problem.



Pin 1: 8.56
Pin 2: 0.007
Pin 3: 0.183
Pin 4: 0.000
Pin 5: 4.27
Pin 6: 7.55
Pin 7: 0.078
Pin 8: 8.58

 

[Perry Babin]

I don't see anything wrong with those numbers. I'd have expected pin 2 to be 0.000 but I don't think it's a problem.

If the PS isn't shutting down, I don't know which protection circuit could be causing the problem.

Does the output drop out at the input of the relays (on output of the output filter inductors) shut down when the amp goes into protect?

 

[Hexhclass]

The output doesn’t drop there is still audio at the input of the relay

 

[Perry Babin]

Are you losing the 12v drive across the relay coil when the amp shuts down?

 

[Hexhclass]

Yes the 12v goes away,I mesured across the diode because the amp is in the sink.
It has two relays am not sure if they in parallel .

 

[Perry Babin]

On the PS driver board, does pin 2 of the 7 pin header go high when the relay voltage drops out?

 

[Hexhclass]

Yes it goes to 12v

 

[Perry Babin]

On the 8-pin IC on the PS driver board, which pin is going high, pin 1 or pin 7 when the amp shuts down?

 

[Hexhclass]

The voltage on these pins doesn’t go high.

 

[Perry Babin]

Is the voltage across the B+ and ground terminals dropping significantly below 12v when the amp shuts down?

 

[Hexhclass]

The voltage goes down to about 11.40v when it shutdown

 

[Perry Babin]

Can you maintain a voltage well over 12v while driving the amp to higher power?

Does that prevent it from shutting down?