CTC-5 21AXP22 convergence

[miniman82]

Originally Posted by Penthode

The biggest drawback of the CTC5 in my opinion is the low high voltage coupled with the relatively dim (compared to tubes a few years later) 21AXP22A.

Low anode voltage is a big problem with the 5 chassis, which exacerbates brightness issues with a CRT that isn't as efficient as later ones.

If I get the time, I would like to explore further the Horizontal Output/ Flyback to see if I can get a bit more HV.

Already have: I added drive and HV controls to my Wingate, nothing I did got any more than 22kv out of it and it was still saggy. Lack of current at the anode is just as big a problem as lack of voltage.


There are two things I have yet to try: installing a solid state 3A3 replacement, and feeding the horizontal section more B+ by using silicon rectifiers in the power supply. I would still run the rest of the chassis on the 5U4 rectifiers, only horizontal would get a boost. I've come to the conclusion that the flyback in the 5 has higher primary D.C. resistance, which means you can only sink so much current into it at a given B+ value. Can't change the flyback windings, so the only thing you can try is feeding it higher amplitude pulses. This may in fact lead to higher anode voltages, but I'm not sure what effect it would have on sweep width and so on.

Another possibility is subbing another flyback, but that's not an easy chore.