Things I have learned this week (Tek-wise)


scoper796 <scoper796@...>
 

Saturday is always a quiet day for me, and so I now have a place to
post some misc ramblings. What have I learned this week? Let's see.

The big one I guess came from spending several hours trying to track
what looked like an oscillation in the horizontal amplifier of a 502.
I used classic signal-tracing techniques using my 545 shop scope. It
was quite high frequency, and no matter what I did, it seemed to just
appear. Pulling tubes didn't make any difference. Finally, I noticed
that whenever I brought a scope probe near the (unshielded) high
voltage board, the probe picked up huge amounts of the same signal.
In a moment of clarity, I realized that leaving the shielding off the
hi-volt section was the source of the "oscillation." Man, it sure
feels good to solve a problem, doesn't it.

I learned that you can wash a scope out pretty good with a garden
hose and not hurt anything. It IS wrong to assume that baking the
scope in the wife's oven at 160 degrees for hours will not give
everyone in the house a headache though. And that a rack-mount 504
will not quite allow the oven door to close. LOL

While cleaning the mess out of the second 547 I received made by the
foam backing for the filter turning back to Texas crude, I scrubbed
and scrubbed with lacquer thinner. Then I fell to the patio from the
fumes. Never assume living through chemistry is better, even outside.

And once again, I learned that the description of an item on eBay,
and my description of it when I get it, represent two different
points of view. And that a $10 item never costs $10 by the time it
finally gets here to Canada.

Happy hunting!

Larry Christopher

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