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From: klem kedidelhopper on 25 May 2010 13:11
Last Winter I repaired a D board in a 32 inch Sony set. I replaced the
two chips with DB versions and the set worked fine for 3 months. It
eventually came back for an intermittent start up problem. It seems
that at times it would just not power up with blink codes alternating
between sometimes being 6 and at other times being 7. The most
frustrating thing is it would sometimes go for days or weeks with no
problem. I posted this a few weeks ago and received some additional
information about an electrolytic capacitor which also should have
been replaced at the time the chips were and I subsequently did that.
After about two weeks of no problems I returned the set. It is now
back again for the same intermittent start up problem. This time
though I noticed something new. There are several components on the
board I worked on whose leads show signs of electrolysis, as though
they were wet when this set was powered up. I recalled that the first
time the customer picked the set up it was raining moderately. We
covered the set and I always caution them that if they even remotely
suspect that a drop of water could possibly have gotten inside to not
power up the set for a few days until it dries out. Whether or not
they ever heed this advice is always suspect especially in this case.
I'm reasonably sure that if there had been corrosion on that D board
originally I would have certainly noticed it. So my question is: is
it possible for corrosion to work its way into a hermetically sealed
component such as a semiconductor and mess with the substrate to the
point where the component becomes unreliable and circuit parameters
change? The corrosion is really not that bad to the point where it is
"hairy" green growing between the leads however it looks blackened and
dark green and it has traveled up the leads of the affected components
right up to onto into the body of the device. The board itself is
fine. Any input on this would be most sincerely appreciated. Lenny.
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