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Old 2nd July 2014, 01:25 AM   #1
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Default Another Sure Board Fried?

Please help. I am supposed to provide music for a big off-grid Independence Day party but I think I did something uniquely stupid and fried my amp.

I have the 4x100W TK2050 module (AA-AB33182) from PE. It was powered by a 12V SLA and was working beautifully. The problem came when I attempted to add an active XO between the source and the amp. The XO is for cars and also runs on 12V, but I managed to switch the polarity on the power connection. I had:

BAT+ to XO- and XO ground
BAT- to XO+

Seconds after powering on, the XO started smoking. I unplugged everything quickly but it appears it damaged the amplifier through the RCA connections. The board still lights up and the fan turns on, but no sound.

Is there any reasonable fix for this or do you need a PhD in electronics to find all of the damaged components? If not, is there any way to get another board by Friday?

Thank you for the help!!!
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Old 2nd July 2014, 12:01 PM   #2
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Do you see any obviously toasted components or burnt traces on the amplifier board?
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Old 2nd July 2014, 12:09 PM   #3
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No, nothing obvious. There was one absolutely charred 1/2 watt resistor in the XO, but nothing visibly wrong with the amp. Of course, half of the board is covered by the heatsink.
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Old 2nd July 2014, 04:32 PM   #4
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Then I wouldn't really know where to start without poking around with an oscilloscope. :-(
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Old 2nd July 2014, 04:53 PM   #5
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OK - thanks for trying. Any idea what sort of damage this abuse could cause? I'll take the heatsink off tonight and see if anything looks wrong under there.

I ordered a new board and paid almost as much for expedited shipping. Yeehaw.
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Old 2nd July 2014, 05:39 PM   #6
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Just guessing, but I think the inputs are coupled through capacitors so there might not have been much damage there. Unless they are electrolytic caps that do not like reverse polarity.
Perhaps there was just a lot of current flowing through the ground traces and the outer ring of the RCA connectors. Off hand I can't think of any particular failure mode other than frying traces and blowing fuses. But I'm no expert either.
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Old 2nd July 2014, 06:53 PM   #7
gmarsh is offline gmarsh  Canada
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Your best bet is probably to just order another amp with the fastest shipping possible. Chances are you've got a blown TC2000 or two.
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Old 4th July 2014, 12:41 PM   #8
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For all of you on the edge of your seat, the replacement module arrived yesterday afternoon. Three cheers for PE. Thanks for everyone's input.

I now have two of these boards I've ruined in different ways. I was thinking I could cannibalize one to repair the other, but I can't imagine any human could desolder and solder these chips with so many tiny little legs.
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Old 4th July 2014, 01:21 PM   #9
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Sounds like you have a ground loop issue. You must isolate everything (all audio paths) when trying to operate from a common D.C. supply..

I fried a few things before I figured it out. Toasted a brand new TV by connecting a simple amp from the headphone jack to power a couple of external speakers! (I was sick!) Isolation transformers are my friend now..
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Old 4th July 2014, 01:54 PM   #10
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The class D amp chips do tend to have tiny pin spacing.
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