Click image to Enlarge the image

This is the amp, Planet Audio VX2200D Class D amplifier	The inside, looks normal, but has a really bad smoked transistor smell
Output Mosfet section of the amplifer. Looks okay	Another shot of the output section
Mosfet Power Supply section of the amplifer. Looks okay at first glance...	Another angle, you can see if you enlarge the pic there is a little sign of a smoked mosfet under the last heatsink clamp.
Overhead shot of power supply If you enlarge the pic, then zoom in, you will notice discoloration of the circuit board and some obviously burned legs on most of the power supply mosfets. Sure sign this power supply has failed.	Another overhead shot of the power supply Discoloration and burned legs not noticable in this pic
Clamps off, it's obvious if you enlarge and zoom in, burned and cracked Mosfets	Another Angle, Enlarge and Zoom in, massive power supply failure
Another angle. Notice the burned mosfet residue on the clamps that I left in the amp for the pic	Closeup, obvious massive mosfet failure
Overhead shot	This is where things get VERY different in the way the amp is repaired at dB-r vs. Hack shops We take the amp completely apart to repair it
A view of the bottom of the circuit board	A shot of the heatsink pads where the burned mosfets were. These will be cleaned up, inspected, and any that need to be replaced will be replaced.
A closeup of the bad transistors from the bottom	A closeup of the heatsink pads
A closeup of the burned mosfets. Enlarge and you can see at least 1 of the legs are completely burned from most of the mosfets	Enlarge here you can see we cut all 16 of the bad Mosfets from the board, the legs will be removed next
Legs are now removed, holes will be cleaned out next	Holes cleaned out (except the last 3 for demonstration) in preparation for new transistors to be put in place
A distant shot of the holes cleaned out	Closeup. Most hack shops would have simply cut the legs off the bad transistors, then soldered the new transistors legs onto the old transistor legs sticking out of the board. This causes problems. The globs of solder can arc over voltage from one transistor leg to another, and any vibration will easily break the solder joint over time. Not to mention it looks like total ass... We take pride in our work and we are not out to make a quick buck...
Cleaned the residue off the board, ready for new IRFZ46N's x 16	New IRFZ46N mosfets soldered in.
Closeup	Looks Factory Original
Overhead view While installing new FET's, any discolored Gate Drive Resistors are checked to see if they are still very close to the same resistance as the other Gate Drive Resistors.	Now before we put it back together, we do do preliminary testing. Amp is turned on, current draw is checked at idle, then a small input signal is applied and a speaker is used to listen to determine if everything is sounding okay, and an oscilloscope is used to check power supply waveforms and DC rail voltage levels, and for the presence of any distortion in the DC rail voltage. Input signal must be VERY small for this test without the heatsink.
Output Fet's removed. During preliminary testing, lost a few output mosfets. Noticed that they were mix-matched date codes. Amp didn't appear to be worked on before, so maybe factory used mismatched codes, or it was a refurb job or something.	Called customer, explained that it needed additional parts, he okayed the extra $$$, parts on order.
New Output FET's Click to Enlarge Image, notice all same part numbers and Matching Date Codes These parts are substituted for IRFB31N20D They are a Drop-In replacement Same part, better availibility	New Output FETs installed!
Another View	Ready to Reassemble
Entire Amp board ready to assemble, Looks factory Original	Spread some fresh heatsink compound on the insulators and heatsink
Spread some fresh thermal grease on the new Fets and other parts	Drop the Board in the Heatsink
Reinstall all the inside screws and clamps.	Done! Ready to test!

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