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! |