[dtvmcdonald]

My previously 100% reliable ct-100 broke today. I turned it on
for a football game and after running about 30 seconds,
with sound but no picture (due to, as it turns out, to the video
cable being disconnected from the modulator) I turned it toan
unused channel and saw the usual snow at the usual brightness.

It then emitted a "snap" and the picture (and raster) was gone.

A quick check showed no HV at the connector that goes to
the CRT anode. More checks showed no horizontal drive.
(The horizontal output tube is fixed bias so it can't red-plate.)
There is B+ on the plate of the horiz output tube (removed until I get drive.)
The fuse in that system is OK.

Checks on the horiz osc with both voltmeter and scope
showed NO B+ on either side. Vertical system works OK.

There is B+ on the plate of the horiz output tube (removed until I get drive.)
The fuse in that system is OK.

There is no B+ on the plates of the vertical convergence amp!

This would all explained IF ... and here I'm using the Sam's schematic
because the RCA ones have the vertical centering control in the wrong place
for my set ... IF Sam's have a 2.5 amp fuse-+-+++ M3 in wrong line
OR if some circuits including the horiz oscillator are put in that line rather than the high power horizontal
one a 5 bolts more positive (which feeds the and it were blown. Well, its blown. After lots of looking yes, both Sam's and RCA have th horiz osc
in the wrong line.

I checked various things running at either of those two voltages (except
the parts clearly in the higher voltage line,
incluing horizonal output.

I then replaced the fuse and, with the CRT and hiorizontal
output unplugged, turned it on. It ran for 2 minutes
whgen I shut it off, no problems, and the horiz oscillator
woked properly.

As far as I can tell the only things running off this line
are the horizontal oscillator and the CRT screen controls.
The vertical convergence amplifier is said to, but that's
not the case in my set, it runs off the fused B+ in the horizontal area.

I did note that the purity control that is in series with this fuse
is open at the high end, but it is run wwell into the working range.

Could the problem be arcing in that purity control or the
three CRT screen pots? What do you CT-100 gurus recommend
I do before turning it on the the horizontal working and/or the CRT connected?