My CT-100 lost HV (from losing one B+ line).

[dtvmcdonald]

Originally Posted by jr_tech

Perhaps isolate the different branches of the circuit with several smaller fuses....the fuse that blows might point you in the right direction.

jr

That's a great idea. However, it would require great thought to
prevent circuit damage. I don't think a fuse that blows in series with
the CRT divide chain would hurt anything. It would put essentially zero volts
on all the CRT screens, and the 100K resistors in the DC restorer circuit
would cause the CRT 1st grid currents to rapidly go to 200 uA by clamping,
which is harmless. I had to so a simulation of this to convince myself.
This is harmless even with the screens being the same voltage as the cathodes,
as the cathode-grid voltage would be only a few volts.

A fuse blowing on the vertical system would be a problem, as it would
generate a single horizontal line at "usual" brightness. I suppose
I could run it a very low brightness. The horizontal oscillator fuse blowing
will warm up the horizontal output tube and transformer
with a bit of DC, but not a huge amount, since the horizontal output tube is
fixed bias at about 30 volts in absence of drive.

I could try it every day on the bench with the CRT and yoke (hence, B+
for the horizontal output) disconnected. That means I would have to move
the two boatanchors there now to their final stations ... they are far heavier than
a CT-100 chassis.