Please explain how a bad flyback can cause the fault described by the
original poster.

Picture size .. blooming .. is caused by high
voltage changing. Generally when the solder
joints start going, it occurs across all the power
handling connections, and at the flyback. Also,
the electrolytics tend to crap out and lose their
capacitance .. even to dead shorts. I've been
into lots of crts where all I did was touch up
solder connections and replace electrolytics
.... and the thing ran fine. Of course that did not
fix the gassy crt which starts the picture to
blur. TRUTH: I've had people come in and say
"just make it work. I'll pay the cost. I like my
crt". So, I clean it ... resolder a bunch of
points .. replace horizontal output transistor
.... replace flyback ... run tube through phosphor
restore and degauss ... set flyback focus ..
dark level ... remove and test all the big
electrolytics, and replace a bunch of them
.... replace the the transistor amps and current
limit resistors on the crt board ... put it back
together and clean the case and screen to
nearly new ... and charge the lady 3 hours
labor at $65 per hour plus parts .. and hope
to heaven that the 90 day warranty holds :-)

johns