6 Jun
2009
6 Jun
'09
2:59 p.m.
Warren Wolfe wrote:
But, when I fired up the 'scope, I was shocked.
He was right. The
scope image could be focused, but it never got clear. It looked like
the phosphor was painted on the tube with a roller. Then, I had to
laugh....
I took off the bezel, pulled off the graticule screen, and peeled the
tyvek sticky paper off the back of the plastic screen, and voila! A
nice clear trace.
As a kid, my first scope (a low-end tube-based TV servicing scope) developed a
problem with 60Hz noise in the trace, that is, even with the V input shorted,
there would still be a slight 60Hz sine wave on the trace rather than flat. The
problem was intermittent as well. Opened it up (of course the problem went away
when opened), tried to diagnose it as much as possible (now that I didn't have
a scope to diagnose with).
No luck.
I suffered with the problem for ages, then finally clued in that my bench/lab
power supply - which of course contained a power transformer which of course
would generate a magnetic field - was sitting on top of the scope, just above
the CRT.