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Old 07-25-2013, 08:38 AM - Thread Starter
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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!
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Old 07-25-2013, 09:02 AM
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The thin plastic is an insulator to isolate the heatsink, you need it.
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Old 08-21-2013, 09:26 AM
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It's fairly simple. The answer to your first question is, you don't need to know anything new. Just make sure you don't use too much solder for any joint or it'll get shorted to nearby DIP connections. The answer to your second question is that you definately need the heat sink as @SAM64 said. Thirdly, the thermal paste is used to evenly distrubute tenoerature across a surface. So in case your amplifier gets really hot, it's easier for the heat sink to work as the complete surfance gets equally heated up. You can use the same thermal paste that you use with your PC's PCB. It is recommended but not critical, your circuit can work without it too I suppose.

pcb manufacturing and assembly
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Old 08-21-2013, 11:32 AM
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Another option is to consider getting a completely new plate amp. If you blew this little op amp, perhaps the answer is to give the sub more power with a bigger plate amp.
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Old 08-22-2013, 07:59 AM
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The easiest way to replace that amp is to get a good pair of sharp flush cut wire cutters and cut each lead of the IC long enough to enable you to heat the soldered side and at the same time pull the cut lead out with needle nose pliers. Then clean out the holes with solder wick or a solder sucker. Then clean off the old white heat sink compound on the insulator and heat sink then re apply new compound. Clean the leads of the new IC. I use a fiberglass brush. Before soldering in the new IC make sure the IC is lined up with the mounting holes. Hopefully you can solder the IC after you mount it. Before re soldering, snip off any excess lead length. This will give you another clean spot for the solder to cling to. Dirty leads lead to bad connections down the road. Good luck.

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