Prototype set is here

[Steve McVoy]

Nick, do you have extension cables to connect it to a CT-100 chassis?

[miniman82]

No, Bob does. The only thing that will be required is the longer anode wire, everything else should reach. Did you get hte chassis yet?

[Steve McVoy]

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

[kvflyer]

Originally Posted by Steve McVoy

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

Steve, your assessment of the "later mods" certainly makes sense. I am just glad that this wonderful piece of history did not get put on the dump as so very many wonderful sets did in years past...

[tubesrule]

Originally Posted by Steve McVoy

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

Steve,
So then you will be restoring this as a CPA set? If so is there any chance that at least the sweep and decoder sections could be working by the convention? I can get started on developing a CPA converter.

BTW does anyone have the actual spec for CPA? Can we assume that most things just match NTSC (burst length, phase and position) and only the R-Y inverted every other frame?

Darryl

[Pete Deksnis]

Originally Posted by tubesrule

BTW does anyone have the actual spec for CPA? Can we assume that most things just match NTSC (burst length, phase and position) and only the R-Y inverted every other frame?
Darryl

Darryl

Fink, Television Engineering, 1952 edition shows the "color-phase synchronizing pulse" in figure 417 on page 549, which may help.

Pete

[tubesrule]

Originally Posted by Pete Deksnis

Darryl

Fink, Television Engineering, 1952 edition shows the "color-phase synchronizing pulse" in figure 417 on page 549, which may help.

Pete

Hi Pete,
I have Fink's other books but not that one. Could you scan the relevant pages?

Thanks,
Darryl

[Pete Deksnis]

Originally Posted by tubesrule

Hi Pete,
I have Fink's other books but not that one. Could you scan the relevant pages?

Thanks,
Darryl

Here's a photo of the page.

Pete

[old_tv_nut]

Steve, I agree that your assessment makes sense, although you would be surprised at some of the breadboarding techniques I have seen over the years. We had one fellow (X) who built prototypes by soldering a 3-dimensional haystack of parts onto a tin sheet. (His soldering was good, not cold joints.) Once it worked, he would unsolder all the ground connections from the tin sheet and put the haystack in the cupboard above his bench. These were known in the lab as "(X) piles."

[miniman82]

Good thing he didn't do paperwork, you could have called them "X-Files". LOL!

[Einar72]

Better a well-diddled prototype than dozens of revisions once in production! Ask the techs who test, cal, diagnose and repair them!

[Steve McVoy]

I don't know how much I can get working by the convention. There are lots of cut wires and dangling components. If I can figure out where everything goes I may get most of the set working.

[miniman82]

Originally Posted by Steve McVoy

I don't know how much I can get working by the convention. There are lots of cut wires and dangling components. If I can figure out where everything goes I may get most of the set working.

Biggest thing will be figuring out what's up with the pulse regulator. I was only ever able to get about 5kv out of the flyback, but it didn't burn up either. That says to me it's probably still good, but the regulator was dragging it down. Once you trace that part of the circuit, we'll know more.

[miniman82]

Stands to reason the burst should not be on a pedestal then, if issues were encountered. The receiver could be modified to work that way, in the event it was built for the burst being on a pedestal. Circuit mods would likely be minimal.

[tubesrule]

Nice catch Pete.

From the article it sounds like it was a certain monochrome set that had trouble with the burst being in the sync area, not the CPA set. I'm also getting out of this article that they changed the burst to ride on the black pedestal for NTSC not for the initial CPA. I guess it's easy enough to just make this switchable in the converter

Darryl