25v vs Roundie

[DaveWM]

Just thinking out loud here...

I wonder if a 25v would fill out a roundie mask. I have some good strong 25v and while always on the look out for a roundie, I was wondering if a 25v could be pressed into service. Of course the yoke would be needed, and the lack of pin cushion would fall beyond the mask so figure that would not be an issue. I imagine the shape of the CRT face would prob not work out either. Like I said just thinking out loud, and down stream when roundies become more rare but 25v's may still be around. mounting with out major gaps would prob be the biggest impediment as would not want to foul up a good bezel just for a temp fit of the wrong CRT.

took some ruff checks of dimensions its just barely tall enough, width looks ok. how it would fit vert would prob depend on the mask, I have noticed some are more generous in the opening size than others. I have some left over mask floating around here somewhere and some 25v's. if no one has already checked, I will try out and see how close a fit they are.

[sampson159]

we tried this in the old shop days.the yoke and pincushion was a problem.i wasnt
involved personally but joe and another tech was.i dont think they got it to really work.it did show a picture but had many strange problems.good luck,you should try it and succeed!

[DaveWM]

well you can be sure if I get that far there will be a video. Even if I can get to work electronically the mounting will no doubt be a big problem. I need a bezel that is not going to have to be destroyed to make it fit. I have a CTC-16 bezel that I plan to see how it would fit. I was thinking if it can work in a test jig I should be able to make it work, but then again in a test jig where pic convergence and pincushion would not have been an issue.

[DaveWM]

one thing I could do is review my GE tab book. IIRC the GE designed roundie chassis had a tacked on board that converted the roundie to a 23v. I think it was just the tacked on board that was added and the rest of the chassis was exactly the same.

[dieseljeep]

Originally Posted by DaveWM

one thing I could do is review my GE tab book. IIRC the GE designed roundie chassis had a tacked on board that converted the roundie to a 23v. I think it was just the tacked on board that was added and the rest of the chassis was exactly the same.

The was more to it than that.
The flyback was different, to satisfy the different sweep angle. The old roundie had a 70 degree sweep and the 23V had a 90 degree sweep. The board that was added was a pincushion corrector circuit.
It's apparent in all the CTC15 clones, that were built for the rectangular CRT's. The pincushion corrector circuit was added and the flyback was changed to accommodate the wider sweep angle.

[DaveWM]

The more I think about it the more I think I will wait until the time when I don't have any option. I mean heck I could just stick in a CTC-17 chassis (I was thinking about a CTC-12 thru 16 set) and be done with it. oh well like I said just thinking out loud.

[ChrisW6ATV]

Maybe try a close comparison of the CTC-17 versus CTC-16 (or CTC-20) schematics. There might be some good clues there.

[DaveWM]

I did just that, not much, mostly the adding of a picushion transformer, but maybe a change in the fly as well. I think part of the problem would be the top and bottom pincushion, as there is no coverage of the mask there, and I assume with the sharper deflection angles you really need pincushion correction all the way around. I am just going to back burner it for now, If the occasion arises I way at least see how the CRT would fit.

[dieseljeep]

Originally Posted by ChrisW6ATV

Maybe try a close comparison of the CTC-17 versus CTC-16 (or CTC-20) schematics. There might be some good clues there.

The CTC20 chassis was in a class of it's own.
RCA engineers took a newer design, entry level model, CTC19/24 and made a roundie model, to use up cabinets, bezels and CRT's.
The flyback was special to that chassis and was an order item.



I worked on a 20 that had a real hi-end cabinet, intended for a CTC16X.

[Jon A.]

Dunno how big of a screen would actually be needed, but maybe SVGA monitor guts could be shoehorned in there:
http://www.videokarma.org/showthread.php?t=260276