fried 800w audiobahn

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well,a couple months ago i bridged my amp and turned on the bass boost knowing i shouldnt have(stupid)to see what it would do and my amp started to smoke so i turned off the boost.Amp was playing fine for about 10 seconds and then a flame was comming off of the board so i put in 5 new of the 8 transistors that were fried and reinstalled it.Today i had the pwer wire plugged in it and i was plugging in the ground wire and as i touched the ground wire to its terminal it sparked and i heard something in the amp sizzled again but no flame.i took it apart again and nothing seems burnt but the smoke was comming off the transistors again
and the copper wire spool inside.help me,please
audiobahn a8002t
 
http://www.audiobahn.com/products/2005Products/amps/amps.html

It is a class D amplifier.

It is also available in the first link I found on Google for less than $200.

You will find it possible that a professional repair shop may charge at least that to repair your unit. From the questions you ask, it is highly unlikely that you will be able to repair your amplifier at this time. Study a great deal, and you will be able to MAKE your own in 6-24 months from now.

Class D amplifiers often use a type of circuit called an inverter to shift the 12 volts available in your car to as many as several hundred volts so that you can get more than single-digits of watts out of the amplifier.
 
I'm not familiar with automotive class D amps, but does it have the usual power supply arangement? With those, the +12V goes to a fuse,a PI filter with a coil and some caps to reduce the junk the switching supply radiates, and then that goes to the center tap of the big toroid coil. Each of the "ends" of this winding will go to a bank of a bunch of paralleled MOSFETS which alternately switch the ends of this winding to ground. The remote line provides power to a PWM IC that provides gate drive to the switching MOSFETs. The PWM IC drives a pair of totem pole small transistors (usually TO-92 smallish ones) that do the grunt work of driving the capacitative MOSFET gates. On the secondary side of the transformer, the Center Tap is grounded and the ends go to either some TO-220 dual diodes or a bridge rectifier module.

Most class AB amplifiers work like this, and are very easy to seperate into power supply, output stage, and preamp. I'm not sure if your particular class-D amp works like this (do they all have the same general circuit layout?) , or if it "directly" goes from 12volt input to speaker output in one stage.

For a class AB amp (and yours if you can seperate the power supply and power amp circuit blocks), if the amplifier blows fuses/smokes/catches fire as soon as the power wires are connected, even when nothing else is connected and there is no remote power to tell it to turn on, you have a blown power supply. Typically the MOSFETs short out. I'd also test the reverse polarity diode (the one that's in there "backwards" to pop the fuse if you reverse the power wires) just to make sure it hasn't shorted, but that's a very remote possibility. If the MOSFETS blow, you have to replace ALL of them. I'd also replace the one's on the other side just to be safe. They're cheap. If the MOSFETS were nuked, I'd also check the MOSFET drivers transistors to make sure they didn't short. Diode tester on a multi-meter is real handy. Remember that without the remote line energizd there shouldn't be any drive to the MOSFETS and no current should be drawn. Also, the preampand power amp will not be powered up unless the power supply is energized so they shouldn't be causing the problem (but that doesn't mean that it's good, either)

When you get ready to test it out again, don't use any speakers (at least not ones worth a damn), and replace the fuse with a small one-say a 5 amp one, so that you don't pop all those nice new MOSFETS in something else is wrong.
 
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