Complete Walkthrough of a Normal Repair


Planet Audio VX2200D
Walkthrough of a typical repair, the way WE do it.



Came in with bad smoke smell. Customer said smoke came out of it, and it quit playing.

This time I took pictures the entire way through the repair process so you can see how dB-r repairs amplifiers, step by step. We do the job right. Unlike our local competition, which I consider a "Hack Shop". I'll give you a hint, it starts with a "K" and ends with a "g". You figure out what letters go "in" between.


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!



Hope this Gives you a good idea of the work we do at dB-r Electronics.
We do it right!