Fixing my MRV-1507...

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I picked up a broken mrv 1507 for cheap...

Right now I'm using a modified xbox power supply, ~12v at ~13amps. Don't laugh, it works well for its intended purpose.

I don't have much equipment at home, but I have access to just about anything I need at work

Is there a service manual/schematic available?


Symptoms:
Power light: not on. It might come on when I first hook it up.
Music light: solid green
protection light: solid red, not flashing
Fan is spinning

Where should I start?
 
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Channel 1 is probably causing the amp to go into protect mode. You need to begin checking the output transistors in that channel. If they are not the problem, you probably have a leaky driver or pre-driver transistor.


I didn't find any shorted transistors when I checked last night...

I will bring my O-scope and a better meter home tonight to poke around some more


I do component level repair work for a living, but I mostly deal with digital circuits...:eek:
 
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All of the input transistors measure 106ohms from pins 1-3(gate to source)

It seems a little low considering there's a 680ohm resistor in parallel.


The board looks like it's speckled with flux underneath. :eek: I expect this out of a $5 knockoff amp, not a $texas one...


The output transistors measure 18.5k ohm.


There was a thin sheet of plastic under each of the input transistors :confused:
 
Those are the power supply FETs, not input transistors.

If you look at the diagram, you'll see that there is a 10 ohm, 100 ohm and 75 ohm resistor skewing the readings.

The plastic was likely mica and is there to insulate the tab of the transistor from the heatsink. They should be under all transistors or other semiconductors with an exposed metal tab.
 
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