On Wed, 23 Nov 2005 12:28:03 -0800, "andrew queisser" andrew.queisser
at hp com wrote:

My trusty Pioneer A-9 has a problem on the right channel. If I listen on the
headphones the sound is great, on speaker the sound is fuzzy but only on the
right channel. The headphone ouput actually comes from the speaker output,
not the preamp, so it seems that fundamentally the signal is getting through
but under load it gets fuzzy. I can hear the distortion in the headphones
when I click the speakers on but when I click the speakers off the sound is
fine.

The power supplies feed both channels in parallel so I doubt it's a power
supply problem.

I have a scope and a little audio probe gizmo that lets me listen to audio
signals with an earphone. I can generate signals from my PC and feed them
into the amp, if that helps. I also have the schematics so I can trace the
signal but I'm not quite sure how to go about it.

Any tips?

Thanks,
Andrew Queisser


Try feeding a 400 HZ square wave into it and see what comes out
(compare channels)

If the leading or falling edges look funny describe the bad one.

I'm not familiar with the A-9 but some discrete amps used to use fuses
on the speaker terminals so if the amp shorts it won't set fire to the
speaker cones. The fuse holders or fuses would corrode and cause
distortion when the current was higher (speakers versus phones).
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