[Penthode]

This evening connected my breadboard circuit to the CT100. The first thing I found was the waveform on the plate of the 12AU7 inverted compared to the waveform printed in the service manual. This means I will likely have to invert it with another stage. Nevertheless I connected it up and was measuring voltages and looking at waveforms. I powered down and up again and found the MOSFET gate to source had shorted. I tried installing clamping diodes on the gate and replaced the MOSFET only to find it shorted. I found that the B+ shot up to just over 500 volts before the tubes warmed and as they were 500v fets that spelled their demise.

Anyhow, without the vertica dynamic convergence correction, with resistor feeding the convergence and focus electrodes only, the focus and convergence did not look bad. The worst was at the top which I feel touching up the vertical linearity will address. The two photos attached is the set running with no vertical convergence transformer. Only the 560k and 330k resistors substituting for the convergence transformer secondary.

I have buttoned the set back together while I think this thing through.

Post thought: Because the vertical convergence transformer has only a minimal effect on the convergence, it is conceivable that a replacement may be installed with a reversed phase primary which may not be noticable. Certainly I saw no impairment in focus and the convergence except for the very top is remarkably good.