Ct-100

[Tom Albrecht]

Had to take a few days off from this project. Too many radios/TVs/hi-fis came in and the shop was filling up. Got those done, so back to this set.

With the current condition of my flyback, I decided to follow up on this great idea that was suggested way back on page 1:

Originally Posted by Electronic M

On newer roundys (like CTC-16 era) I've heard of folks having successfully removed the fly's HV winding and getting their HV from a solid state HV trippler the input of which being connected to the HO Tube's top cap....This may also be a solution for your CT-100.

...

Good luck fixing it.

Gave it a try this evening. Pulled the TCG523 tripler that has been serving very nicely in my Philco 48-2500 projection TV, and wired it up to the CT-100 chassis. I've got the HV winding of the flyback coated with a relatively thick coat of insulating red varnish, with the end of the HV winding buried in the varnish. That seems to be working OK to keep the HV winding from arcing right now. If this ends up being a usable solution, I'll coat it even better, or possibly remove it altogether.

The first picture shows the tripler on the bench temporarily wired up to the chassis. The input of the tripler is connected to the top of the primary -- the same place the 6BG6 plate is connected. The ground connection of the tripler is connected to the chassis, and the HV lead is resting against my HV probe.

Fired it up, and got 26-27 kV at the tripler output (see second picture). Putting the focus rectifier in place to provide at least a little load for the flyback lowers it to around 24 kV, which seems like a really lucky break. Just about right. The focus rectifier is wired as it originally was, off its own tap on the flyback, and powered by its own filament winding. The 3A3 HV rectifier is removed, and its filament winding not connected to anything.

Connected the tripler output to the HV regulator circuit in the set by touching the HV lead from the tripler to the metal housing of the 3A3 socket. The HV regulation works fine. If I set it to 20 kV, I get a mild red glow from the inside of the 6BD4 regulator (similar to what I had before at lower voltages when I was using the reduced-output flyback). Third picture shows the setup and the HV probe reading. I can adjust the HV from 16 kV to 22 kV with the CT-100's HV adjustment pot.

This looks like it may be a viable solution for dealing with my bad flyback. Will try it with the CRT next.

By the way, don't pay too much attention to the way I've got the replacement convergence transformer hanging off the back of the chassis. I will pot it in the original transformer housing once a few other issues are out of the way here.