Isn't the buildup of static charge the reason CRTs get dusty - attracting
dust - and also why sitting in front of a CRT TV or computer monitor bad
for those with allergies?
On Mon, Dec 7, 2020, 14:18 Ed Breya via groups.io <edbreya=
I second Eric's suggestion, especially regarding the "back of the hand"
test, which makes a great static charge detector. With a small CRT like in
a scope, you can just place your knuckles against the CRT face.
If the CRT lights up and seems to operate normally, then eventually the
sound should go away as the static charges in the materials equalize. The
root cause may be that you did too good of a job cleaning the face parts. I
have often said that dirt and grime can be your friend, when it comes to
static electricity problems. After a CRT has been in service for a while,
ambient moisture and particles form a natural static discharge path on the
surfaces. If you've used an anti-static wipe on the plastic shield, that
should have similar effect. Maybe try the same on the CRT glass face too,
and be sure both sides of the plastic shield are treated.
Of course, this all assumes the sound really is just discharge at the
face. If it's something else inside, then it's a different story. Try
looking at the scope, opened up, in the dark. Sometimes you can see
discharges around the HV parts. Also, if there's enough, you can smell
ozone and nitrogen oxides in the vicinity.