Memphis Audio (MOJO 2000) 16-2000D Repair


Memphis MOJO 2000 Amplifier



This one came in from someone in Austin, Texas. He told me other shops in his area said it "could not be repaired". Of course I begged to differ. So he sent it to me. And I had it working right away, but it was still in very bad shape, needed a complete rebuild, and all of the "rigging" that the other shops had done to it removed.



Click image to Enlarge the image



This is a shot of the main board. Doesn't look that bad from this view,
but check the zoomed in pics below.

Next to the goop of silicone you can see a soldered bare wire there...
Not supposed to be there.

Right in the middle of this pic, next to the burnt orange color capacitor
you can see a blue wire soldered across a black resistor.
Not supposed to be there, and could cause problems in the current sensing
circuit.

Sixth FET from the left is mixmatched, not even the same manufacturer.
This is another NO-NO!

Some of the output FETs were bad, and caused some problems with the driver
boards so they are removed and some small diodes and transistors replaced.

Here you can see nice clean removal of the driver boards from the main board.

A closeup of the driver boards. Some of the diodes and transistors are in
need of replacement.

Now we remove the output FETs and all those rigged up wires and resistors.

Outputs removed and all "ghetto-rigging".

A closeup, top side. Looks nice now. Ready for new parts.

Bottom side of the board without outputs and rigging removed.

The black resistors that say HMR on them are part of a current sensing
circuit in the amp. They are important and should not have had a wire
across them. The protection circit did not kick in quick enough in this
particular amp, and therefore some of these very low resistance resistors
were damaged. See pic below:

That hole in the bottom of that resistor is not supposed to be there.
These resistors will need to be identified and replaced with heavier duty
parts.

A pile of bad parts.... this amp needed major work.

And the replacement resistors installed. Much heavier parts, these are 5
watt, the originals were 1 watt.

Nice how I lined them up...

Another shot, looking good...

We go ahead and change the power supply FETs too. Even though they were
still good, we went ahead and replaced them at the customers request with
higher current handling parts than the factory used. This will make the
amps power supply more stable with higher current.

New power supply FETs installed.

New power supply FETs installed, ready for output FETs.

All new FETs installed!

Reinstalled into heatsink.

Another shot.

Load Test!



It has been 2 months and this amp is still working great for the customer. The other shop was so confident that the amp could not be repaired, that they placed a wager (bet) with the customer that no other shop could repair it. Well, they were wrong (of course). Customer won the wager, and they paid for the repair of this amp.