fosgate x200.4

[bdgf2004]

i forgot to add that when when i disconnect the scope from shield fround it will pull a signifigant amount more current

 

[Perry Babin]

Are the shield grounds on the RCA jacks broken?

 

[bdgf2004]

no, i've checked that. if i connect the shield to the chassis it's ok. i use my computer for audio. in a vehical the shield will be connected to ground via the radio.

 

[Perry Babin]

How do you define 'chassis'?

 

[bdgf2004]

ground terminal

 

[Perry Babin]

With no RCAs plugged in, what's the resistance between the input RCA shields and the main ground terminal?

 

[bdgf2004]

~1000 ohm

 

[Perry Babin]

That's normal. Have you checked the shield on the signal source to confirm that it's not open?

 

[bdgf2004]

im so sorry i gave you the wrong numbers.

i only get .5 ohms between shield and chassis

 

[Perry Babin]

If it's 0.5 ohms, D3 is shorted.

Are you sure the meter was set to ohms and not diode check?

 

[bdgf2004]

you're right d3 was shorted.


i replaced it and now i have ~1000 ohms between shield and chassis.


thanks

 

[Perry Babin]

Is the amp working better (less noise) than it was before?

 

[bdgf2004]

no, it's still the same. the distortion increases significantly as i increase the volume until i connect the shield to chassis then it plays perfectly.

 

[Perry Babin]

Is the distortion audible or are you only seeing it on the scope?

 

[bdgf2004]

audible

 

[Perry Babin]

Is the ground for your signal source connected to the amp ground?

 

[bdgf2004]

i'm using my desktop computer for the signal source.

 

[Perry Babin]

Is the case of the computer connected to the amp ground?

 

[bdgf2004]

no, everything is just plugged into the wall.

i'm actually using the headphone jack on a cheap (wal-mart) set of powered speakers for computers. they are plugged into the wall and to the headphone jack of my desktop.

 

[Perry Babin]

I don't think you can do any meaningful troubleshooting until you get a proper signal source. You have too many variables, any one of which could be the cause of the problem.