Memphis Mojo 2000W amp blown power supply - diyAudio
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Old 23rd January 2010, 06:43 PM   #1
m4ick is offline m4ick  United States
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Default Memphis Mojo 2000W amp blown power supply

My friend blew a mojo 2000. looks like missing supports broke a rectifier and mosfet causing the power supply to fail.

i replaced the driver transistors (KTA1266s) and all 22Ohm resistors.

I thought these amps came with IRF3205s in the power supply, this has all IRF1010Es.

Which is the original part or can they be substituted?
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Old 23rd January 2010, 09:32 PM   #2
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In some of these amps, 3205s were used but I can't tell you if all of them used the 3205s. I'd use the 3205s instead of the 1010Es.
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Old 23rd January 2010, 10:03 PM   #3
m4ick is offline m4ick  United States
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New rectifier, new irf3205s in, it protects (power and protect lights on), rectifiers out it comes out of protect. are 22ohm gate resistors still right?

there are no shorted outputs (didn't thoroughly check the driver cards, no oscope). it appears that physical damage caused this because a rectifier was cracked in two.

if i let it warm up some w/o rectifiers the two largest resistors on the driver card get warm, not hot at all, just warm. is that odd?

could I check for peak voltages where the rectifiers were so I can tell if it is PS or output?
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Old 23rd January 2010, 10:06 PM   #4
m4ick is offline m4ick  United States
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it has been fixed before, there are mismatched date codes in the outputs but they all seem within tolerance of each other, none are shorted.

that's how the 1010Es probably got in there.
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Old 23rd January 2010, 11:57 PM   #5
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With the rectifiers in, do you see a pulse of DC voltage on any of the 4 output filter inductors just after you apply remote voltage?

You'll need to have the meter connected to the inductor before you apply remote voltage because the pulse could be very short. Monitor the voltage for about 10 seconds for each inductor.

It's normal for the driver boards to run warm.
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Old 24th January 2010, 06:33 PM   #6
m4ick is offline m4ick  United States
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the inductors show ~-25mV and then cycles from 0 to ~-25mV.
the power mosfets get very warm, I wouldn't want to run them for more than 10 sec.
nothing else seems to get hot quickly.

16V supply drops to 6.5V, so the power is going somewhere. filter caps did not test shorted.
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Old 24th January 2010, 10:47 PM   #7
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You stated that nothing else gets hot quickly. Is there a group of output transistors that begins to heat up more quickly than the rest?
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Old 24th January 2010, 10:52 PM   #8
m4ick is offline m4ick  United States
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all output transistors stay very cold. all power supply fets get fairly evenly warm (i.e. no banks are hotter than others).

I'll double check the outputs for heat so disregard this post till then.
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Old 25th January 2010, 03:21 PM   #9
m4ick is offline m4ick  United States
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OK! Outputs are as cold as ice! But.... on the inductor side of the rectifiers, diode test sees 001, when you push the inductor one way it opens, the other it shorts. Sounds like the insulation on the inductor wires is worn from heat or vibration. That would explain why only PS fets get hot.

Can I repair this inductor (unwind and patch)? Never patched an inductor, wanted to know if there is a specific method. If not, is it the same inductor that is in the Orion 2500D? I can't afford to fix the orion yet so it can be used for parts for now.
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Old 25th January 2010, 03:33 PM   #10
m4ick is offline m4ick  United States
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don't know if you care but i have to tell everyone. a system I built went to the import face off yesterday. he wasn't going to go but somebody with 12 10s was really running their mouth.

well, my buddy showed up with the system I built for him and beat EVERYONE AT THE SHOW! he averaged 150.2 w/ 6 pioneer 12s and 2 JL1000/1s. took home three trophies including loudest car of the day, street beat, and 1001-2000W. had to post it, very excited. you can see the build at my site TooMuch Audio.

thanks for your help Perry. i'll post again when I have the inductor out. this amp may end up in that car again after all.
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