27 Sep
2008
27 Sep
'08
9:53 a.m.
Gordon JC Pearce MM3YEQ wrote:
Tony Duell wrote:
I would be reluctant to float a delicate instrument at several kV.
Can't this damage the instrument through corona discharge around some of
the internal components?
Philip.
I am wondering about measuring the average beam
current when
displaying the level 15 raster of each primary colour and making sure
it's reasonable. Beam current is near enough the final anode current,
so measuring that would do. But that would mean having a microammeter
floating at 25kV wrt earth. What fun...
I haven't seen the circuit, but I'm guessing you'll find some handy
resistor around the cathode to sample the voltage across. Obviously
this will be somewhat high due to the grid currents, but my gut feeling
is that they won't be significant compared to the anode current.