In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:

That tends to feed my predjudice that the protection circuitry tends
to bring with it a set of additional 'failure modes' and sources of
problems.
:-)

Indeed. I'm hoping it isn't so clever it won't power up unless it sees
exactly the right load. I've spoken to the ex-owner who says the noise
from one rear speaker was a loud but intermittent crackle. My hope is
it's a (simple) amp fault causing the DC speaker protection to trip.

The "intermittent crackle" is the kind of symptom I associate with a poor
joint or a componment degrading and causing the bias levels to be quickly
wiggled about. If you also see an output dc level that jumps about a few
10s or 100s of mV when this happens I'd say that was a candidate.

If so, a quick shuggle (wiggle or poke) of various components or spray with
freezer may show up the culprit. Or threaten them with a close encounter
with a soldering iron. :-) If you are lucky it is just an internal
connector that needs a clean.

FWIW My one annoyance with the Yamaha CT7000 FM tuner is all the
expletive push-on connectors used for links between boards, etc. After a
decade or two these tend to go intermittent and need unplugging, then the
pins and sockets cleaning, then replugging. If you are lucky that is the
cause and will be easy to fix ... until it happens again in X years time.
:-)

If you are unlucky it is an internal connection in a device and be
reluctant to show up with freezer or a shuggle. In the end I only found
this with my amp by replacing one individual device at a time until I found
the little devil.

Slainte,

Jim

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