"CJT" wrote in message
...

There are several possibilities, including (in no particular order) -

SNIP
aging of the CRT
SNIP

How can aging of the CRT result in picture blurring ?

I know that kathodes or heaters could wore out or that phosphor could decay,
but what effect would cause blurriness ?

Most of the units I have seen got that way aither due to HV pots (for focus
and screen) and due to demagnetisation of the calibration magnets and rings.
IOW, nothing that couldn't be trimmed and retweaked...

Branko