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-   -   Prototype set is here (http://www.videokarma.org/showthread.php?t=251369)

Username1 06-15-2011 10:22 PM

so is the face of that tube a greyish or a little greenish in color. More like the color of the early 15GP's or more the color of the 21axp's? I wonder if the 1b3's meant the tube was designed to have lower beam current. Too bad there ain't a Sam's you could order for that chassis.

NewVista 06-15-2011 10:45 PM

Quote:

Originally Posted by Eric H (Post 3006211)
You're got to be kidding, this tube tested good!! :thmbsp::thmbsp:
Can it be plugged into a working CT-100 chassis to see if it works.

Still can't be sure until HV or tesla coil present; the getter is a bit worrisome.
But if there's no faint blue neon glow anywhere along guns (viewed in dark) with tube tester, that would be promising.

miniman82 06-15-2011 10:54 PM

From what I learned by using the CR-70, a tube with air will peg the needle after advancing the cutoff control beyond a certain point. You reach the ionization point of the gas inside, and then you get full conduction. Exactly that happened with the 21AXP22 that was in my Director 21, purple neck to boot. But this one is fully variable throughout it's entire range, and the needle rises slowly as it warms up just like it should. So I'm optimistic about it, but we won't know until some HV can be applied.

miniman82 06-15-2011 10:56 PM

Quote:

Originally Posted by Username1 (Post 3006213)
so is the face of that tube a greyish or a little greenish in color. More like the color of the early 15GP's or more the color of the 21axp's?

It looks greenish to me, kinda like the 21AXP22 in my CTC-2B. I have it parked right next to the CTC-4 at the moment, and it's very obvious the difference when viewed right on. The screen on the 2B almost glitters, while the one in the 4 just looks like plain paper.

Dave A 06-16-2011 01:14 AM

This is real history if only the 6-bolt CRT is functioning.

Eric H 06-16-2011 02:06 AM

I think the next question is not if this set can be made operational but IF it should be.

If it's an RCA Prototype it truly is a signifigant piece of history, replacing capacitors and other components would seriously compromise it's historical value IMO.

David Roper 06-16-2011 02:29 AM

I think there's historical value in being able to see just what a dot-sequential or proto-NTSC electronic receiver was capable of. We've now been able to see what the CBS sets were capable of for quite a few years, but when they first came back to life it was quite a revelation.

Phil Nelson 06-16-2011 02:32 AM

I have mixed feelings about whether to restore it and I can think of good arguments for both sides.

Personally, I would find it hard to resist making it work. It was designed as something to be used, after all, not a museum piece.

I would soothe my conscience by doing nothing invasive, restuffing paper caps as well as electrolytics, maybe even finding resistors that look more period-correct. Ideally, when it was done, it would look the same (at least to a casual eye) but WORK as the designers intended.

Just my $0.02.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Electronic M 06-16-2011 02:53 AM

I agree with Phill's suggestion for how to go about electronically restoring it.
Better to keep it looking original if you restore it IMHO.

Tom C.

ChrisW6ATV 06-16-2011 03:37 AM

Quote:

Originally Posted by miniman82 (Post 3006209)
Anyone wanna hear how the variac powerup of the chassis went?

If you do get a matching or near-matching schematic diagram from Ed Reitan, you may be able to do just that after some electrolytic restuffing. Absent that schematic, you could draw your own (got a few days or weeks?) and compare it to the CTC2 schematic to maybe narrow down the missing or incorrect tubes.

Either this forum or my browser needs to be taught some of the words we use around here. It doesn't like variac, powerup, or restuffing.

Pete Deksnis 06-16-2011 06:07 AM

Quote:

Originally Posted by old_tv_nut (Post 3006203)
The adventure begins! Have you determined at all if this could be a dot-sequential prototype rather than early NTSC?

I wondered that too. Based upon a reading of Wentworth and Fink plus the preponderance of 1952 tubes, I don't see now how it could be a dot sequential set using three-state communitator circuitry. However, I couldn't resolve one way or the other their flirtation with phase alternation in that time period. So, it probably uses equaband quadrature circuitry for chroma, bypassed luma (of course), in 1952 perhaps a nonstandard color subcarrier frequency, and maybe PAL-like circuits.

My two cents.

Pete

cwmoser 06-16-2011 06:22 AM

If it were mine, I'd want to restore it to working condition using reliable modern capacitors. Save the removed parts.
But, I would take multiple high resolution detailed digital photos of the entire chassis as documentation history of the set.

You are now part of this TV's history.

Carl

cwmoser 06-16-2011 06:25 AM

Do you have any information about where this TV has been over the last 60 years?

Carl

MelodyMaster 06-16-2011 06:34 AM

Quote:

Originally Posted by Pete Deksnis (Post 3006239)
I wondered that too. Based upon a reading of Wentworth and Fink plus the preponderance of 1952 tubes, I don't see now how it could be a dot sequential set using three-state communitator circuitry. However, I couldn't resolve one way or the other their flirtation with phase alternation in that time period. So, it probably uses equaband quadrature circuitry for chroma, bypassed luma (of course), in 1952 perhaps a nonstandard color subcarrier frequency, and maybe PAL-like circuits.

My two cents.

Pete

But it appears that the set has been used over the years http://www.videokarma.org/showpost.p...8&postcount=24 So it was either built as 3.579 quadrature, or has been modified to be NTSC-compatible.

Steve McVoy 06-16-2011 07:41 AM

I really doubt if the set was used over the years. The only evidence of that is the tube date codes, which is tenuous. I don't see any other components that look newer than 1952 ish.

Congratulations on having what appears to be a working tube.


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