5FP7 project starting with the focusing coil.

[AdrianPH]

Jeffrey;

Thanks for the response.

I am more than a bit confused at this end, my mind is finding something difficult.  Not helped by the figure I was using for the transformer inductance was the figure for the focusing coil?

I took a few more measurements again before tea/dinner.  The transformer measures as follows: -
primary inductance 5.6 H
secondary inductance 92mH
scan coil inductance 61.2mH

Then I stick them all together with the secondary connected to the scan coils and measure the primary side and the inductance is 3H.  So even if I use 3H with the formula  V =  L * dI/dt

The primary side current is sweeping a change of 20mA and the flyback is 0.23mS I would get a voltage of 260 volts.  So I have taken the transformer out of circuit and done a simple audio sweep of the primary side to look for a resonance and found one at around 8.4KHz, which is close to twice the flyback frequency, I can not really tell if that is the best as I do not have a suitable audio gen that I can sweep.  I am just basically trying to figure what the transformer is ringing at, looking at the spikes in my picture, the time of one 'spike cycle' it would seem to be approx 0.4mS which would make it around 2500Hz, the horizontal divisions were 1 mS.  OK I can not tell what effects the valve and the rest of the circuit would have.

You seem to suggest that adding a bit of capacitance across the transformer may help so I will revove the resistors and try a few small values such as 100, 270 pf and see what effect they would have, unless you can suggest a value?

Anyway, play time again.

Adrian