Another Westinghouse H840CK15
 

I found this one semi-locally. Missing knobs but everything else appears to be there. I don't have a real way to test, but the getters on the CRT at least appear to be OK. I'm going to try to get this thing working little by little starting with the horizontal sweep section and go from there. Lots of paper/wax capacitors in here! You all think I should try to maintain appearance and restuff the paper caps or just say screw it and put the modern yellow ones in there? I don't see where any components have been changed on the bottom of the chassis, and most of the tubes appear to be original Westinghouse (mostly rebranded RCA and GE) except the horizontal output tubes and one 5U4. One question: Is the chassis copper plated or is it just some sort of copper colored coating?

Serial number MW005779, chassis number ME000552

I hope you can restore this TV to its peak condition, as this was the first color television receiver to be marketed in the United States. (You can test it if you have a VCR, DVD player, or a cable box.) I did a Google search on the model number and found a site which mentioned the price of this TV was just under $1300. This meant not many such sets were sold; in fact, most of the sets Westinghouse manufactured that year did not sell for that reason and, not surprisingly, there was very, very little color programming on the 3 networks (NBC, ABC, CBS) at the time, so even folks who owned this particular TV did not see much as far as color shows went; that is, the new Westinghouse TV would display a picture, but in b&w.

Color TV was definitely a status symbol in the 1950s, with most existing TV stations not yet equipped for color telecasting, so even if you could afford this Westinghouse small-screen roundie TV, you would be watching mostly b&w programming on a pitifully small (by today's standards) round screen.

Color telecasting did not "take off" in the US until the 1960s, and even then the sets were prohibitively expensive for most folks, so most stayed with their old reliable b&w TVs; this did not change until later on that decade. Think of when the first flat-screen HDTVs went on the market shortly after the DTV transition of 2009. These sets sold for well over $1000, with very little HD programming available. Now, nine years after the introduction of HDTV, flat-screen TVs, even large-screen models, can be had in some cases for under $100. Early color TV went almost exactly the same route. By the 1960s into the 1970s, color boomed in the US; more and more homes were getting color, relegating their old b&w TV to the basement or rec room or discarding it if the CRT went bad, or the set had developed expensive repair problems. This also is the story of the evolution of today's flat-screen HDTVs and how they have completely replaced analog sets, but that will be material for another thread.

BTW, I am not sure where or even if you will be able to find a set of knobs for your Westinghouse TV. You could put an ad for such knobs on VK's own classifieds section; that failing, I would search eBay or Craigslist to see if one or more of these knobs turn up there. I would try to find a set of period-correct knobs, as this TV was the first mass-produced US color set; it would not look right with just "any old" knobs on the control shafts.

Wow ! Talk about being LUCKY.. As with any/all "1st out of the Box 15" color sets, you likely can count the survivors on the fingers of one hand... Well, maybe not quite THAT rare, but these guys ARE pushing 70 years old (Gulp !) they were temperamental things when new, & spare parts TRULY are "Unobtainium"... But, Man-Oh- Manischevitz getting to have/see one of these actually WORK would be worth ALL the hate & discontent you'd have to endure... IMHO, anyway.

Actually the westy has around 26-28 survivors known so you'd need all your fingers'n toes plus a friend with about half theirs. It is the second highest surviving 15" color to the CT-100 of which somewhere in the neighborhood of 200 still exist.
3rd place seems to be RCA model 5 prototypes at 12 then a gradual slide down to 0-1 known for some. http://www.earlytelevision.org/color_database.html

It is great that more are coming out of the woodwork. The more that we can preserve the better. :thmbsp:

Absotively ! Also glad to get clued into the relatively HIGH number of survivors. Have wondered about someday venturing to greater Nashville, & hitting up the sort of "Downmarket" type antique stores & seeing if any odd ball "Goodies" lurk therein.... Nashville had a LOT of well paid "Industry" types, that were the kind of folks that would buy all the new type "Toys" like color sets, transistor stuff, VCRs, fancy cars, all like that. Its an ENTIRELY different world than we were, here in hardscrabble Greater Bugtussle...

Erich, I am very happy for you (and envious!). Glad that you found this set and it truly deserves a restoration. I also hope that the 15GP22 is good as well. Please, keep us posted.

I got the power supply chassis OK with new capacitors in place of the multi-section electrolytic, but connecting it to the main chassis only found more electrolytics in need of replacement (a B+ dropping resistor started smoking right away). I'm going to have to remove/replace the multi-section capacitors on the main chassis one by one and do a restuff so I can avoid that kind of problem later and concentrate on getting the sweep sections going.

I was reading the other long thread here about the same model TV and saw something about magnets for static convergence. The three screws on my set don't have any kind of magnet on the end and don't look like they ever did. What is this magnet supposed to look like?

These are the 6-32 threaded magnets that are about 2 inches long for the static convergence.

I’m about to post an update. We are in need of one to finish our restoration.

In that case I'm probably OK. The threaded rods are in fact weakly magnetic. I thought it had to have an actual magnet on the inner end.

So far I restuffed the FIVE electrolytic cans on the main chassis (I thought there was four, but then another B+ resistor started smoking and I found the fifth can). Then I powered up the set without horizontal output tubes and verified the sweep oscillators. I had to replace the coupling capacitors at both the vertical and horizontal output tube control grids since there was excessive positive voltage on the grids. Next I installed the horizontal output tubes and everything seemed OK. Lastly I tried installing the CRT assembly back in to see if I can get a raster, but no go. I found normal voltages on the CRT cathode, G1 and G2 and some semblance of high voltage (slight static cling holding paper to the CRT faceplate). No abnormal light show in the CRT neck, either, so that's still a really good sign. Next step is to get a proper HV probe so I can verify the HV, focus, and convergence voltages.

One of the candohm resistors decided to short to the chassis, so I need to find a solution for that. It feeds power to the sound section, so for now it is disconnected.

EDIT: Actually my G1 voltages are a bit high, but that should cause the CRT to go to maximum brightness anyway. Will have to replace coupling capacitors in the chroma adder section for this. Had to go to the Sams folder to find CRT electrode voltage readings.

I got a HV probe so I could trouble shoot the low HV. One of the doorknob capacitors is bad (measured about 1MEG resistance leakage, no good). When I pulled the plate cap on the second 3A3 the HV went from 6kV to 14kV. Repairing this should get the HV where it needs to be. Also during testing the focus control started smoking and got destroyed. I found out I have the dreaded vertical convergence transformer problem which caused the focus control to burn out. So I have three things to take care of before I can move much further.

I'm going to experiment with graphite and epoxy and see if I can repair the focus control. It looks like it's going to take quite a few attempts before I can get something I can use to replace the resistance track. Next I will see if any more reproduction convergence transformers are available. The doorknob capacitor is a bit expensive but available, so no problem there.

I have another idea for repairing the focus pot. The challenge is that the pot can dissipate up to a watt according to some rough calculations. The resistance track is just a bit over 4 inches long and about a quarter inch wide. I need something that can take the heat. I ordered a sheet of .020" phenolic material, now I need to find some way to get a resistive material to adhere to it. Maybe try graphite in a clear lacquer.

If you have a bad screw magnet for a CT-100 or similar, there is an easy fix, which I used.

Just find a small ceramic magnet and break it into various size pieces. Set the
defective screw at a convenient spot, then try pieces at the OUTER end
of the screw until it more or less converges. Then glue it on, and screw the screw until its exactly right. Easy.

Well I have results and some more problems to overcome. I can get picture and sound. I have no color sync at this point. I need to repair the broken coil plug on the hue control and see if that helps. It seems to have normal signal flow in the chroma section when checking with a scope, it just won't sync up. I can get on both sides of the lock point with the color hold control, so that is likely OK.

Next is the HV supply. I was able to repair the damaged focus pot. I made a new resistance track using thin phenolic board and pencil lead. I applied the pencil lead to the roughed up surface of the phenolic strip until I got the correct resistance value. I then installed it in the potentiometer housing. It seems to hold up even when constantly adjusting the control. I had to replace two doorknob capacitors as well. Now I get 27KV and can't regulate it down to normal. Possibly one of the high value resistors is out of tolerance.

Last on the list is the vertical convergence transformer. The reproduction parts are no longer available so I will have to rewind it myself at some point. For now I have wired around it for testing. Of course the convergence is off, but at least I can see how the rest of the set is working.

The CRT may be weak or the kind of picture I'm getting is a result of the excessive HV. It's better than a completely dud tube at least.

I've used india ink for DIY high-value resistors. It would probably work for potentiometer elements too, depending on wattage rating.

Yeah, that was one idea I tried early on for the focus pot repair, but the India ink I tried was a bit too conductive. I laid out a strip on paper and got less than 100K resistance. Now I was able to use it to repair the red screen pot since it arced and burnt at the end of its track where it was riveted. The resistors are available at Mouser, but they're about $20 a piece. I have only one meter (Keithley 196) capable of measuring resistor values this high, but it's in need of calibration for the resistance function and I'm not sure how accurate the readings really are. I calculated the voltages I should get from the schematic, so I'll try making measurements later to see where I'm losing voltage. The voltage at the 6BD4 grid is low (200V, needs to be closer to 300-400V) to get it to start conducting and lowering the HV to spec.

Did you contact John Folsom? He may have a VCT. SEE THE BOTTOM OF THIS LINK: http://www.videokarma.org/showthread...=270450&page=5

Yep, already tried emailing John Folsom, he replied that he has no more transformers available. The one in my set has either shorts or leakage from secondary to either ground or the primary. This one doesn't look fun to take apart or rebuild. Lots of varnish and many thousands of turns of fine gauge wire. I probably won't get an exact turn count out of this. Also looks like the laminations are stacked in alternating directions, so they'd have to be pried off one by one.

Sure is nice to see what certainly appears to be a good CRT! Major obstacle overcome. Thanks for sharing your progress and pictures.

The apparently weak CRT turned out to be a wiring error on my part in the color video amplifier section. I had a coupling capacitor essentially shorting blue and green signals together as well as shunting the green signal to ground. Correcting that as well as going through a few adjustments in the chrome section allowed me to get a color picture at last. The set still does not like displaying very bright scenes, but these sets probably never got really bright pictures to begin with, so I will just keep the brightness down. Color lock is still a bit weak. Still need to come up with a solution for the vertical convergence transformer to get this working like it's supposed to.

Very nice improvement.

And "getting there". I will admit that as a young adult, I really looked down on the round color tube. To make it even more disgusting, I had no knowledge of the 15GP22 Kinescope! Now, I can really appreciate seeing one displaying a color image. So very cool.

I remember the hype about "Rare Earth" phosphorus and thought that this was a remarkable discovery. But red became Chinese Red, not blood red if I under stand correctly. Seems that the 15GP22 and 21AXP22 were the cat's meow colorwise?

Wikipedia has a pretty good writeup about CRT phosphors. The original red wasn't very efficient to begin with, then 80% or so of the electron beam current never got past the shadow mask anyway to even light the phosphors. From what I have read, the original NTSC phosphors were used in the 15GP22, 15HP22, 19VP22, and early production 21AXP22 tubes. The later reds had a bit shorter wavelength and so appeared a bit more orange. The green phosphor was changed somewhere down the line as well, but I don't know when (probably starting with the 21CYP22). The original green is actually the same as the P1 used in old oscilloscope CRTs. Later color TV tubes first used cadmium doped phosphors, then later on the rare earth (yttrium and europium I think) phosphors.

The overall impression I get having read various articles about the subject is that the 15" color sets really were the wrong product at the time. This is when 21" B&W sets were common, and you were going to pay lots of money to get what is effectively a 12" round CRT color picture. Add to that the weird and expensive construction of the 15GP22 and that's probably why these sets were sold at fire sale prices soon after being introduced. The CBS 19" CRTs seem to be even less common than the 15" ones. It took RCA with the 21AXP22 to get color TV sales off the ground, and it still took over a decade for color TV sales to reach 50% of total.

Well the 15G development started around 1950-52 and at the time 15" was the standard screen size so it is understandable why they picked it.

The 19" color tubes only had a few months before being obsoleted by the 21" tubes.

In that case the 15" tubes just ended up obsolete by the time they were ready for the market. I'm curious as to why RCA thought the best thing to do was use the separate internal faceplate in the 15GP22. It's either flat or very nearly so which introduces pincushion distortion. Maybe they thought they'd get best results getting phosphor dots on that kind of faceplate?

This set has been a real interesting experience for me. I never thought I'd run across something like this becoming available, much less with a good CRT.

I believe the flat internal phosphor plate was used in the 15GP22 due to technology being unavailable to create a stable curved shadow mask. The flat mask could be under tension to prevent deformation with temperature. A domed mask had to be mounted on temperature-compensating mounts that moved the mask back or forward slightly depending on temperature (and resulting contraction/expansion) in order to maintain color purity.

Yes, and in addition I believe that the phosphor dots were merely silk screened on the flat plates used in the 15GP22. The photo process to deposit the phosphor on a curved surface, using the shadow mask as a “negative” for exposure had not been perfected when these tubes were manufactured.

jr

"merely silk screened" doesn't quite describe it.

Zworykin and Morton describe the process in "Television" 2nd Ed. 1954. The description seems to be adapted from a 1951 paper by Barnes and Faulkner, but I believe it is the same as in the 15GP22.

Summary:
Produce the original image for etching the mask by exposing a photographic plate to a fine wire grill twice, with a rotation of 60 degrees between exposures.
Careful processing and copying reproduces a negative optical mask with round dots instead of diamond-shaped.
Expose a thin super-nickel sheet coated with photengraving enamel through the negative.
Wash away the unexposed enamel and etch the exposed metal to form the apertures with sharp feather edges.
Heat this mask and attach to the support frame while hot, so it becomes under tension.
For phosphor patterning, prepare a stencil from the mask:
[One stencil will be used for all three phosphors, with a precision displacement between applications.]
Place a Kodalith plate at the screen position with respect to the mask, and expose with a point-source carbon arc lamp placed at one gun position.
Develop the Kodalith plate.
Sueegee a protective coat of lacquer and wax onto the developed plate.
Coat with photosensitive gelatin emulsion, and expose through the plate onto the emulsion with a carbon arc lamp.
Wash away the unexposed gelatin.
Transfer the wet stencil from the plate to printing mesh and dry it.
Squeegee the phosphor suspension (phosphor powder in ethyl cellulose and amyl alcohol) onto the flat CRT glass screen.
Remove the stencil and clean it.
Allow the CRT screen to dry.
Bake the plate to remove the ethyl cellulose.
Repeat for the other two phosphors, with the stencil precisely positioned.
Bond the phosphors to the plate by misting with potassium silicate solution.
Float a nitrocellulose "blanket" onto the plate and evaporate an aluminum layer onto it.
Finally, bake to remove the nitrocellulose.

The thing to note is that the shadow mask was used as a negative, but with the intermediate stage of producing a silk screen instead of direct deposit of the phosphors.

Sheesh, its a wonder they ever got any 15GPs out the door w/all THAT going on...

Wow! thanks for the process details... incredibly more complex than I had imagined when I heard that the phosphor had been “screened” on to the plate. :thmbsp:

jr

I'm sure there were many more details to the production apparatus that you wouldn't guess unless you had it to examine. For example, the book mentions that a special technique (exactly what, they don't say) was used that held the silk screen in contact with the glass plate while squeegeeing so that it wouldn't stretch and distort the pattern.

This is the kind of thing that makes me laugh at people who ask why we can't rebuild the Saturn V rocket today to go to the moon again. It's because the tools are gone and those who developed the secret sauce for their use are too. So we have to start from scratch. Now, we may build something much better, but we still are starting from scratch.

I didn't take many pictures of the focus pot repair, but this is what I have. I got about 6.5MEG overall resistance which should be close enough. The difference between 5 and 6.5MEG is a few quick strokes of pencil lead, so that was my stopping point after having to remove material several times. I drilled out the two rivets holding the outer terminals to the by housing and used small screws to install them after placing the new resistance strip in. So far it has held up to frequent adjustment. Seems that it is necessary to tweak the front panel convergence and focus adjustments almost every time the set is turned on, mostly the convergence control.

Mullard made a film about colour CRT production in the UK. I'm sure techniques had been refined since 1954 but the basic principles are unchaged: https://www.youtube.com/watch?v=0Qd4IX3wpZk

old_tv_nut said:
"This is the kind of thing that makes me laugh at people who ask why we can't rebuild the Saturn V rocket today to go to the moon again. It's because the tools are gone and those who developed the secret sauce for their use are too. So we have to start from scratch. Now, we may build something much better, but we still are starting from scratch. "

Not just stuff as complicated as a moon rocket. Lot of knowledge about older valve and semiconductor manufacture is also lost. And much else besides. Even if it's all well documented, the formal term for "secret sauce" is tacit knowledge, or tacit skills. The stuff that isn't in the books, often passed on by direct experience. Here at VK and other vintage forums we are helping to keep those skills alive.

https://en.wikipedia.org/wiki/Tacit_knowledge

Thanks for the link. Most complete video on the subject I have seen.

As an example, who is rebuilding CRTs now that Hawkeye closed???

Pretty much nobody, as far as anyone knows, unless you have a heavily modified DeLorean someplace. :tears:

At the risk of taking my own thread off topic, I really think the people who have been working with the rebuild equipment at ETF should practice on common B&W and color tubes first before worrying too much about pre war tubes and 15GP22s. Forget the metal cone stuff for now. Perhaps they have been, but all I hear about are attempts at rebuilding 15GP22s outside of that one monochrome tube that ended up with a 12V heater and one 21AXP22. Unfortunately their effort relies on volunteers at this point which limits the manpower available to learn and do the work and get to a point where those high value tubes can be reliably rebuilt at a reasonable price. Heck, I'd volunteer myself but I don't have the time or money to do it. I'm decades away from retirement and over a thousand miles away.

I seem to have found a CRT rebuilder out there, Thomas Electronics at: https://www.thomaselectronics.com/repair-overhaul/

Don't really know what they will charge but it would be worth looking into.

I know myself if I didn't have to work due to retirement and/or if I hit the powerball or something, I'd like to join the ETF CRT rebuilding project to be trained and learn the process. Maybe it could turn into a business to support ETF and VK member's projects and so forth, I don't know. CRT TV's are still desired by people who play videogames so maybe like record players in the last few years, maybe CRT's and/or rebuilding will make a small but significant comeback. Sorry to hijack the thread too but I've often thought about this during quiet moments from time to time. I do agree we need to start with more common and modern CRT's at first and then progress to the older ones. Just my $0.02

Video of rebuilding report from this year's convention:

https://www.youtube.com/watch?v=ObHANbL0zB0

Eric, you have made unbelievable progress in a very short time. Take a bow!!! You have used a ton of creativity in getting things to work.

Regarding the pots you repaired. How did you get the graphite from the pencil lead to adhere to the phenolic board? You had mentioned using a certain type of glue, but I couldn't find the reference when I reread your notes.