[TechAssist] Re: Marantz A/V Receiver - TA135AV - Blowing Outputs
- From: "majorthom@xxxxxxxxxxxxx" <majorthom@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 25 Mar 2004 11:50:52 -0800 (PST)
Since you did all you said[it helps to use a variac turned way down when
playing w/this]It looks like the "ole diff. amp prob" and that is the diff amps
will give off a noise spike or other transient [of high amplitude and
BLAM,outputs are gone.Way I tblsht this deal is w/ freeze spray on each diff.
amp while monitoring offset/idle current.Let me know,Pete
David Lessard <mr_fixit@xxxxxxxxxxxx> wrote:OK, first I should let you all know
that I don't work on many audio
amplifiers, I'm OK with the module stuff, but when it comes to
transistor outputs, I, well, hmmm, we won't even go there! I acquired
this amplifier (broken) many moons ago, at that time I wasn't that
versed in amplifier repairs however I'm learning, a lot. Needless to say
I've been through a few outputs. I think I took all the precautions
before installing new outputs, I confirmed the +/- power supplies, I
checked the emitter resistors, I confirmed there was a good undistorted
signal coming out of the pre-drivers before replacing the outputs, I
reset the output idle current (this might be where the problem lies) and
confirmed there was no DC on the outputs. Still the amplifier will blow
outputs, the last time I didn't even have speakers hooked up, I was
monitoring the idle current and poof. I don't have any specific
information for setting up the proper idle current and I'm not too sure
how to do this. What are some of the methods for setting up the idle
current without information? Or better still, does anyone have the
service manual for this receiver; I would really like to restore this
unit if at all possible.
Thanks in advance,
David Lessard
Alexandria Electronics
Alexandria, Ontario, Canada
K0C-1A0
mr_fixit@xxxxxxxxxxxx
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Peter Neal
Neal Electronics
1905 E. Wm.Cannon
Austin,TX 78756
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