bz wrote:

snip

[if you want to have some fun, dig a hefty magnet out of a magnetron or old
hard drive, mount it on a rubber band, carry it around behind a CRT monitor...

A neighbor tossed a recent model CRT TV onto a rock pile fact down; after
rescuing it and a cleanup and powerup, the CRT showed color distortions
where the shadow mask was dislodged. Bringing a magnet near the neck of
the CRT close to the purity magnet rings, I felt a strong 10 Hz pulsing
about five inches from the tube. Moving the magnet closer than two inches
produced pulses almost too strong to retain a grasp on the magnet.

Not having a schematic of this set, I can only conjecture on the cause.
Do recent model sets have some sort of servoed pincushion correction or
other control loop running at 10 Hz?

Regards,

Michael