Another Westinghouse H840CK15 - Page 3 - Videokarma.org TV - Video

old_tv_nut · #31 07-07-2019, 07:26 PM

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.

trinescope · #32 07-08-2019, 08:21 AM

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.

ppppenguin · #33 07-08-2019, 09:12 AM

Quote:

Originally Posted by old_tv_nut

"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.......

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

old_tv_nut · #34 07-08-2019, 10:16 AM

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

kvflyer · #35 07-08-2019, 01:01 PM

Quote:

Originally Posted by ppppenguin

Lot of knowledge about older valve and semiconductor manufacture is also lost.

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

Yamamaya42 · #36 07-08-2019, 01:23 PM

Quote:

Originally Posted by kvflyer

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.

trinescope · #37 07-08-2019, 02:08 PM

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.

NowhereMan 1966 · #38 07-08-2019, 10:56 PM

Quote:

Originally Posted by trinescope

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

old_tv_nut · #39 07-09-2019, 10:16 AM

Video of rebuilding report from this year's convention:

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

wkand · #40 07-09-2019, 11:04 AM

Quote:

Originally Posted by trinescope

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.

.

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.

old_tv_nut · #41 07-09-2019, 11:07 AM

Thomas electronics is a military supplier. They were mentioned in a thread here in 2014. There does not seem to be any progress in working with them, probably because of both price and the fact that people were looking for someone who could repair pyrex glass tubes. They might be an option if you have a regular glass tube and megabucks.

trinescope · #42 07-09-2019, 12:15 PM

Quote:

Originally Posted by wkand

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.

Thanks for the kind words. I tried mixing India ink into epoxy but that didn't work, probably because the ink is water based and didn't mix well. Also, the epoxy didn't get hard enough to be able to be used as a resistance track, even without anything added. Next I tried adding ground up pencil lead to lacquer, but that didn't work either. I could have tried getting powdered graphite and adding that to lacquer again, but I didn't want to go through waiting for that to arrive, so I went back with my old idea of pencil lead rubbed onto a suitable surface. I initially used card stock for a trial and got a strip which measured almost exactly 5MEG, but since this part dissipates a bit of heat I didn't feel it was a good idea. That's when I started looking for a thin phenolic sheet. I got one that was .020" thickness and looks like thin PC board material. I roughed up the surface a bit with fine sandpaper and rubbed the pencil on it until I got close to the correct resistance. It really didn't take a whole lot of pencil rubbing to get there, and you could see light through it.

NowhereMan 1966 · #43 07-09-2019, 09:50 PM

Quote:

Originally Posted by old_tv_nut

Thomas electronics is a military supplier. They were mentioned in a thread here in 2014. There does not seem to be any progress in working with them, probably because of both price and the fact that people were looking for someone who could repair pyrex glass tubes. They might be an option if you have a regular glass tube and megabucks.

I knew they were more of a military supplier but it seems from the literature they would take jobs, then again, as you pointed out, it could cost a lot. Even so, i figured it was good to mentioned them. Hopefully the ETF people will get a handle for this and perhaps in the future, there will be a small demand for it for others to pop up much like there is a small resurgence in vinyl records. I do see the point though where predicting the future is tough, but who knows, maybe once 3D printing gets more sophisticated.

NowhereMan 1966 · #44 07-09-2019, 09:52 PM

Quote:

Originally Posted by old_tv_nut

Video of rebuilding report from this year's convention:

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

Keep up the good work! If I hit the powerball, I'd like to be trained for this and join in.

tubesrule · #45 07-10-2019, 06:14 AM

Quote:

Originally Posted by old_tv_nut

Thomas electronics is a military supplier. They were mentioned in a thread here in 2014. There does not seem to be any progress in working with them, probably because of both price and the fact that people were looking for someone who could repair pyrex glass tubes. They might be an option if you have a regular glass tube and megabucks.

I spoke with them extensively back in 2014/15. They claim they are capable of rebuilding anything including Pyrex tubes although never provided evidence of this, and that's as far as it went. They would never commit to anything for any price. They basically had no interest in our community. Perhaps someone else could pickup the torch and try contacting them.

Darryl