Prototype set is here
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Here are the first pictures!
The small pics have been uploaded for immediate viewing, for the large file right click/save as on the URLs below. WARNING: picture files are large, 3+mb. Expect long load times. http://miniman82.4t.com/images/proto...t/IMGP4529.JPG http://miniman82.4t.com/images/proto...t/IMGP4530.JPG http://miniman82.4t.com/images/proto...t/IMGP4531.JPG http://miniman82.4t.com/images/proto...t/IMGP4532.JPG http://miniman82.4t.com/images/proto...t/IMGP4533.JPG |
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I did not realize that you bought that set. Congrats! Looks like it will be a fun project! Looks like lots of electrolytic cans in there.
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Better'n Christmas when you were 5 yrs old...(grin)
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First thoughts:
It's obvious they were trying different things with this chassis; there are holes where parts should be, disconnected parts, and it has a generally unkempt look to it. Wires are routed in a military fashion, tied off and specifically placed. Some circuits like deflection and tuner/front end look like standard fair. Others are a complete mystery- I see no evidence of what would be a dead givaway as a standard looking delay line, but there is an empty spot on the underside of the chassis marked 'delay' (see pic IMGP4543.JPG). The HV section is strange- there is a 6CD6 output in one of the sockets (the ST shaped one in image IMGP4536.JPG), but then there's also a 6BQ6 in the socket right next to it. No idea what that's about. Damper tube is a 6W4GT, which seems like it should be the incorrect tube for a color set. Most sets use 6AU4GT(A), so I'm not sure what to think there. HV rectifier is a 1B3, which again seems like small B&W style stuff. Color sets typically use higher rated tubes like 3B2 or 3A3. Same thing with focus rect, which is a 1V2 where most color sets use a higher rated tube such as 1X2B. Picture tube is developmental C-73547, similar to the one at the ETF. Getters look strange to me, I think the tube might have gone to air since one of them is clear in the center. Either that, or they were too close to the glass at the time they were flashed and scorched the glass- I've seen that before on audio output tubes. Other than that, everything else looks pretty good. I now have the monumental task of figuring out how exactly this thing works, and to that end I will be focusing my efforts on the color section first. Bob Galanter has said he will try and stop by this weekend to have a look at it, and I'm hoping Mark will stop by with his tube tester. Much more to come, stay tuned! :thmbsp: |
Very exciting! Are you going to draw a schematic of what is there?
Phil Nelson |
I might not have to, Ed Reitan has told me he may have a schematic from the early chassis somewhere in his library. I just need to wait and see what exactly this thing is, and we'll move on from there.
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Nick, first, thanks for all the great hi-res photos. I am not sure when the 6AU4 was introduced, but this set may perdate its introduction. I have production 15" color sets with 1B3s in them, so it is not unheard of. Probably hard on the poor 1B3s, but they work.
You are probably planning to do this, but I suggest you make a tube chart, listing tupe type/mfg/date code. Also, a list of part numbers on all transformers, as these often contain date codes and manufacturer info. It is anybody's guess if the CRT is still under adequate vacuum to operate, but the signs are encouraging. Of course, my Hawkeye rebuilt 15GP22 tests good, had beautiful getters, and lights up purple like a neon tube when voltages are applied! So you just can't tell by looking. Do you have the missing tubes, or are these going to be part of the mystery? I don't see tube numbers marked anywhere. Are any of the control labels readable? I can't tell from the photos. This a a fantastic set, thanks for sharing. I look forward to your upcoming discoveries. |
:drool:Wow!:jawdrop:
Holy schmit, you are really gobbleing up some ultra-cool rare stuff lately. Your not trying to compete with the ETF, are you?;):naughty::scratch2: Hope you can get it to run. If that happens you might just have the earliest working single CRT non-mechanical color set.:thmbsp: Either way it should be a very interesting restoration. Good luck! Tom C. PS: Now I know what the festive ocasion was, and wow that is one impressive ocaision. |
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You're welcome, John! At some point I should probably stitch them together to make one giant one, though it would take a long time to download. I don't know when the 6AU4 came out either, but I know we had previously speculated on the horizontal output tube- the 6CD6 in this chassis is dated the 17th week of 1951! Most of the rest of them date from '50/'52, with the 1B3 in the HV section showing 1958. Quote:
Yes, it's one of the things on my list. A lot of the parts on this chassis show RCA stamps, so I'm fairly certain this was made by them. Vert output transformer, power supply choke, some of the other RF cans, and of course the tuner are all RCA items along with some of the tubes (assuming those are the tubes it's supposed to have). Quote:
Of course, you are correct. I hope the test this weekend brings good news. I can look through the center of the base, and am able to see a slight patch of green around the evacuation stem which indicates copper corrosion. I hope it has not done any harm. Quote:
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horizontal/vertical hold, power switch/volume, contrast/brightness, and tuner. On the back: Pretty much the same stuff as a CT-100 would have. Purity, convergence, drives, backgrounds, focus, ect. Nothing that would make me say "a-ha!", but I don't know much else about the set at this point anyway. |
After following some wires from the CRT socket, it quickly became apparent that there are 3 tubes (6BL7's) that are driving pins 3, 8 and 18 on the CRT socket (which would be grids on a 15GP22). I assume that means these are the adders or some part of the matrix, but the strange thing is there are also 3 diodes on terminal strips for each one as well. They look like the same type of thing that always seems to get used as a detector in IF strips. DC resto, perhaps?
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I thought the getters looked a little small on that tube too. But it was never meant to live a long life, just test set. I think the same about the 1b3's in later daily use they proved unsatisfactory for color sets. Good luck with it and many thanks for the cool picts!
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John: Almost missed it, but there's a control in the center of the chassis. It's only marked with a 'C', so I assume it's the color control.
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WOW .. this is going to be the most amazing thread... this is real history .... I sure hope you can get the set to come alive... this really is what all this is about. Good luck and congratulations!
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Congratulations on getting to delivered. It should be an exciting project.
The space marked Delay doesn't look like it is in the video section? |
Nick,
Great photos. Glad everything arrived in good order. My money is still on this being an RCA prototype. Look forward to what ever you guys discover. -Steve D. |
Glad it all got there in good shape Nick. Especially that rare proto CRT. Hard to tell what the getter looks like from the photo, but you could check for continuity on the filiments before I get there on Saturday.
I will bring the Sencor and the B&K along with the adapter for the 20Pin bi-decal base. From the photo I can tell the gun assembly is definately of the 15GP22 type with electrostatic convergence cup. It has some centering wings that are spot welded to the cup that are not present on a 15G gun but other than that, the gun is a 15G gun. In the event the crt is a leaker, You could send it to France to be leak sealed with frit glass and re-gunned. John and I will be sending our first 4 15G tubes over there sometime in august. We have special cartons and a crate being built. Each round trip shipment to France and back will contain 4 tubes. |
Good for you Nick. Will enjoy watching your progress. That is quite the set.
Greg |
Congratulations for your acquiring this unique set, Nick. I notice the convergence pin on the CRT socket looks like new, so it must not have had much use, though the 1958 1B3 is interesting.
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I am happy to hear that the RACS 15GP22 rebuild project is moving beyond the one-off stage and into true production. |
One of the things that Harry Poster told me was that he suspected that the previous owner (not a TV person) had plugged tubes in sockets just to sell the set.
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Bob, one of the photos from Harry showed the filaments glowing, so the filament has continuity and the tube isn't fully air.
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The chassis seems to show signs of a normal life and maintenance period during your set's first years in some kind of service. Sprague and Mallory single-section electrolytics and the 1B3 date coded 1958, all suggest a period of "normal" use.
Having no apparent delay line along with a chassis area earmarked "delay" is another unsolved mystery. I gather reading twixt the lines that this set recently came from Harry Poster. He sure has had some rare merchandise through the years. |
The adventure begins! Have you determined at all if this could be a dot-sequential prototype rather than early NTSC?
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This is kinda like findin' Gottlieb Daimler's heretofore unknown SECOND prototype of his 1886 car under a tarp in a dry barn somewhere...
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:banana::banana::banana::banana::banana: Took a little time to wake up, but all 3 guns read at the top of the good scale after sitting for 5 minutes and the life test ain't bad either. Anyone wanna hear how the variac powerup of the chassis went? :scratch2: |
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Can it be plugged into a working CT-100 chassis to see if it works. |
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.
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But if there's no faint blue neon glow anywhere along guns (viewed in dark) with tube tester, that would be promising. |
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.
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This is real history if only the 6-bolt CRT is functioning.
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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. |
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.
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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 |
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. |
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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. |
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