Audiopipe apsm-1300

[imraneesa]

Hi all,

This amp was in protect. Changed outputs and the amp comes on but seeing -1.5v on output terminals without signal. When signal given it is still having same -1.6v but when I increase the gain until it clip the voltage disappears (with no load).

 

[caraudioguy2100]

Did you also replace the driver transistors for the outputs ?

Could possibly be a leaky driver transistor

 

[DArends]

Have you tried hooking up a load? I have a RA tivo 1000.1 that does the same until u hook up a speaker to it

 

[imraneesa]

Amp running cool and no drawing of high current. Checked small transistors on mainboard and all look normal.

 

[Maxikill97]

Is there a voltage difference between speaker terminal - and speaker terminal +?
Or do they both have the mentioned -1.5v on them?

 

[Perry Babin]

What's the DC voltage between terminals 1 and 2 of the driver board?

 

[imraneesa]

The voltages between 1 and 2 of driver board is 0.004v.

 

[imraneesa]

Is there a voltage difference between speaker terminal - and speaker terminal +?
Or do they both have the mentioned -1.5v on them?

It is voltage difference between - and + output terminals

 

[Perry Babin]

Was the DC drained (as previously suggested) when a load was connected to the speaker terminals?

 

[imraneesa]

Yes the voltage decrease after connecting load. But the amp going into protection as I increase volume. It going now into protect with and without load before the volume even reach 1/4th

 

[Perry Babin]

You said that the voltage decreased with a load. Did it go to 0v?

Does the output look clean up to the point where the amp shuts down?

Does the amp draw significant additional current with a signal but no load at the point where it shuts down?

 

[imraneesa]

It is not going to zero, I getting voltage like 0.5v. But suddenly it blew the outputs. There is some problem. Oscillations are all good without input. But once signal is given it goes into protect. Some times as I increase gain it goes to protect. I dont know what ic the driver board is using for me to change and try. 4 ic are in driver board I guess is opamp.

 

[Perry Babin]

I don't understand:
4 ic are in driver board I guess is opamp.

 

[imraneesa]

I meant out of 4 the one with 8 pins is an opamp.

 

[Perry Babin]

On this type of driver board, I've seen the NJM4560 and the LM6172 used.

 

[imraneesa]

What about the two ic in the extreme right?

 

[Perry Babin]

See attached.