Help with replacing component on circuit board

[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 and a plastic insulator on it.

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

Question #2: 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!

 

[duke37]

If you are sure that the amplifier is faulty, then the best way of removing it is to snip the leads with a side cutter and remove each wire separately. Use a solder sucker to get rid of most of the solder and braid to remove the rest.

The heat sink paste does not glue surfaces together, the components should be mechanically clamped to the heat sinks. They may be electrically connected to the heat sink or may be insulated. Make sure you replace as found. The heat sink compound should cover as much area as possible and should be as thin as possible. It is there to conduct the heat and is not very good at it but is much better than air. Fix to the heat sink before soldering the new amplifier as it can be difficult to change the position if you get it wrong.

A lamp in series with the input power can limit the current and stop fuses blowing. Once the amplifier is working then it can be directly connected to the mains.

 

[KrisBlueNZ]

Excellent answer duke37!

 

[davenn]

If you are sure that the amplifier is faulty, then the best way of removing it is to snip the leads with a side cutter and remove each wire separately. Use a solder sucker to get rid of most of the solder and braid to remove the rest.

ohhh its definitely faulty ... look at the huge hole blown in the top of it in pic 1

Dave

 

[marcus_clarkus]

thanks for the input guys. And duke, that's a really good idea to attach the IC to the heatsink before soldering it to the board, I'm sure you just saved me a lot of frustration and time

 

[KrisBlueNZ]

It's not just a good idea for that reason. It minimises force on the soldered connections to the device pins. This is a very good idea, since pins on hot components are already prone to dry joints. So it's also best for long term reliability.

 

[marcus_clarkus]

I got it working, thanks for all your help!

 

[duke37]

Excellent, glad to know that you have been succesful.

I have a Sony audio system here which had an argument with a thunderstorm and the amplifiers have blown apart. Will have to get a round tuit !

 

[elebish]

Good advice Duke! Ed.

 

[marcus_clarkus]

3.5 year update: subwoofer still works great after my fix. thanks again duke!

 

[(*steve*)]

If you're coming here from the polkaudio forum with a different question about this subwoofer, please don't post in this thread.

If your subwoofer is "coughing", then this might be the thread for you.