Need help repairing subwoofer (found internal short on PCB)

[marcus_clarkus]

Product: Polk Audio PSW202 powered home theatre subwoofer
Problem: Blows fuses in matter of seconds
Solution: Found component causing internal short, need advice on replacing it

burnt Audio IC amp-

I'm fairly sure that the darkened solder on the bottom of the board has not come into contact with anything it shouldn't have.

amp without aluminum cover-

Picture of everything (aluminum cover in place)-

So the little audio amp on the circuit board burned out and I need to replace it with this:
Audio IC (mouser electronics)
Question #1: I've soldered wires before, is there anything special I need to know about soldering a circuit board?

Also, the heat sink for the amp was in contact with a large, aluminum enclosure and had some thermal paste on it. The thing that confused me though was that there was a thin piece of clear plastic stuck between the amp and the aluminum.

aluminum cover, note the plastic piece held in place on it with thermal paste-

Question #2: Do I need the thin piece of plastic to separate the amp and the heatsink?
Question #3: Can I clean the surfaces (as I would on a PC's CPU) and reapply thermal paste that is meant for a PC's CPU?


Thanks in advance for any answers/advice!

 

[fatboytyler]

Question 1: Be careful not to overheat the board, so try not to stick the iron on the board for too long. Try nnot to bridge anything. Other than that its pretty simple.

Question 2: I feel like if it was there in the beginning do it again. It could have been there because the paste was conductive (I have no idea honestly). Or it could have been there for the sole purpose of keeping it from scratching it.

Question 3: I don't see why you couldn't. All those thermal pastes work the same way if I am not mistaken.


Side Notes: I am a little wary of that burnt spot on the bottom of the board. It may cause you some problems.

Other than that, good luck!

 

[makkem]

Hi
I have experience with audio amps.
That power IC you are replacing has the supply voltage on the heatsink bracket,the purpose of the plastic shim is to insulate it from the heatsink (aluminum plate) which is most likely connected to ground and will cause a short if not used.
For the same reason do not use cpu thermal paste which often contains silver or copper and is conductive.You will need non conductive thermal paste.