Ok, i know this is probably a dead thread. well it is untill now.
I would make sure your xtant is getting at least 11 volts.  get a vol
meter or a multimeter and check it at the amp.  the light will turn o
but it wont produce any sound if its below 11 volts i believe.  as fa
as the fan problem, w/ my 3150 the fan does not turn on untill the am
starts to heat up some.  then it will turn on its not constantly on. I
will quiver and twitch when its getting warm.  when it heats t
whatever it takes to turn it on it switches to full speed.  7vol
muting are you talking about the noise gate?  turn it off fo
diagnostic purposes

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Madblunte