Help with 9T246 Horizontal Linearity

[dtvmcdonald]

I think I should start a new thread for this problem, here in the right place.
I got an RCA 9T246 at the 2013 ETF conventions. Its recapped and working
quite well except for a very bad horizontal linearity problem. The horizontal area
has been partially re-resistored.

The picture is stretched at the right, which extends off the screen. The
left side is squeezed up and slightly wrapped around (i.e. the image starts
appearing during retrace.) There is a blank space of about 1/2 inch or so
at the left side. The nonlinearity ratio is therefore huge. The width control
was lacking a core so I tried two different ones, both of which work. However,
neither the width nor horizontal linearity controls have a large
effect if adjusted, though they do have some small effect. The previous
owner said that the horizontal linearity coil was getting hot, but I checked it
and at most its getting very slightly warmer than that general area of the set.
When I first turned it on there was a slight "hot coil" smell, but that
went away before I could sniff out the source.

I checked that all capacitor values are per the Sam's schematic and checked
all the resistor values I could around the horizontal area, and they are
correct. I checked the waveform between the oscillator and output tube,
and its as perfect shape as can be. I can't tell if its the right size since
Sams gives only the shape, not the voltage. Finally, I noticed that the
horizontal drive control, a shunt trimmer capacitor from horizontal output
tube grid to ground, is wide open (i.e. adjusting it makes the width smaller
and the wraparound worse.) This latter makes me think that a possible
problem is that the drive for the output tube is too small.

What should I try next? I think I can come up with replacement output
and damper tubes. Would it be worthwhile to try replacement width and
linearity coils if these can be obtained, or even generic replacements if
somebody knows the approximate values? These same coils seem to
be used in lots of RCA sets of that era. Would measuring the waveforms
and/or voltages at different places around the horizontal output be helpful?
Could (heaven forbid!) it be a bad flyback? One more idea ... could some the
values on the Sams schematic for this group of sets be wrong for the
particular 28C chassis that the 9T246 uses? The two capacitors on either
side of the linearity coil have values identical to those on the 630 schematic,
as do the listed width and linearity coil resistances.

Doug McDonald