Question about Marantz PM7200 2-Channel Amplifier
Hi, After quite a long time I started my amp and immediately noticed that the sound is badly distorted in the speakers. Tried to fiddle with the controls a bit and when I switched off the Class A button the fuse blew off (the one in the back-left side of the amp). Changed it, but it blew off again when I started the amp. When switched back to class A its working but distorted as described earlier. Regards, Kris
The class A switch adjusts, via an optocoupler, the bias on the output transistors.
I would check the standard bias and class A bias adjustments.
Posted on Mar 22, 2014
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Posted on Jan 02, 2017
The distortion might be caused by a resistor. The loss of volume could be the capacitors, but you could try injecting signals into the transistors to see if any has gone. They can cause the distortion and loss of signal. If you apply a soldering iron to any part it will heat up quicker, or you could also use a hairdryer for the whole thing. You can also get a freeze spray that cools things that have heat sensitive faults (available from electronic parts shops).
Posted on May 04, 2009
SOURCE: Hi, i have a marantz
There are one or more transistors failed in the output circuit
I would have tech look at the amp and see what the power supply is doing without spkrs connected
Posted on Aug 20, 2010
Testimonial: "Hi Petraman7, Cheers for your reply i think your right, i'll have to have a tech guy to look at it, any idea how much it could cost. Cheers Paul C"
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