distortion noise from powerbass xa-1500d

I just purchased this amp from the pawn shop for $125 and i suppose i couldn't hear the noise at the time cuz the guy who was testing it before i paid for it had the gain max'd out and used 8 gauge power wire when the amp has 1/0 terminals. While playing music there is a noise like the coils in the subs are rattling, i've used 4 different subs and still the same results. I've used contact cleaner to clean all the audio adjustment pots and can't remedy what's causing the noise. Does anyone have any suggestions? Thank you for any and all help
 

Perry Babin

Member
Paid Member
2003-11-20 11:01 am
Louisiana
www.bcae1.com
For reference, this is one of the other versions. Can you see how close they are? But not identical. This is why I ask for photos of the exact amp.

You need to follow the signal from the RCA jacks back through the op-amps to see where the noise enters the circuit. If you don't know the exact path, start by checking at the output terminals of all of the op-amps to see if any have the noise.
 

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got a few pics of what i've found so far. I tested what i know with what little experiance i have with troubleshooting. This is using a hantek pc based oscilloscope auto calibrated, playing 50hz tone from my ipod touch

[IMGDEAD]https://i269.photobucket.com/albums/jj41/jeff_macon/a00e7ca9-46db-4a97-b6d7-4b8862a7ecf7.jpg[/IMGDEAD]

the 4 drivers(a1023/c1027), gate resistors and 2 pins(7&8) scoped like this indicated by green
[IMGDEAD]https://i269.photobucket.com/albums/jj41/jeff_macon/20160514_135445.jpg[/IMGDEAD]
2 other drivers scoped differently(indicated by red
[IMGDEAD]https://i269.photobucket.com/albums/jj41/jeff_macon/20160514_143310.jpg[/IMGDEAD]

i'm not entirely sure of the voltage path during audio input, I have a few TL494CN opamps if i need to replace it.