12LP4 cathode ray tube autopsy
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- Опубликовано: 15 дек 2024
- I recently picked up a TV with a dead picture tube and a quick test showed an open filament. Let's take a closer look.
Picture tube rebuilding at Hawkeye. The last US rebuilder shows us how it's done: • The Craft of Picture T...
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ブラウン管の復元が出来るので驚きでした。天才しか出来ない作業です。このような努力は大変素晴らしいと思います。💯👍
CRT is the grandest of all tubes.
A cleaner way to de-neck the tube would be to insert a ten gauge copper wire into your soldering gun and wrap the wire around the neck tightly>>don't overlap the wire. Energize the gun and in a few seconds the concentrated heat will crack the glass in a line around the neck.
Very interesting and educational a first time seeing the inside. Many thanks Mike
ive wondered how a small projector would look firing at the back side of a crt lens.. something to try someday.
Good golly! Getter goes goodbye right in front of your eye. Amazing it still does what it supposed to do after 75 years.
I’ve always been curious if there would be any merit in reflashing the getter if the tube was found only to be gassy. Flashing with a small induction wand/ oscillator could be done easily.
Possibly, but only if there is some unreacted material left in the getter cup.
@@bandersentv Some getters are in the form of a tiny trough formed into a ring. The material is loaded into the trough.
That was awesome. I've never seen anyone do a video like this explaining the electron gun in real time.
There are at least a couple of videos about this on RUclips. It is very unfortunate that no links are allowed in comments. There is one by "Applied Science" from 13 years ago using a oscilloscope CRT. Another one is by "tuopeek" from 4 years ago about Television Cathode Ray Tubes. Search and you should find.
Neat! Always wanted to try that. You saved me the trouble and resultant mess. Thanks Bob!
Thank you; very interesting!
I had a tube that also had an open filament, having nothing to lose, I zapped the pins with a charged capacitor to try & weld the broken ends together , after 4 attempts I had continuity.
Testing the tube proved that it now had cutoff & emission, albeit not great, it was tried in a set & did produce a picture.
My theory was that surge voltage from the series string had weakened the filament over it's lifetime, eventually causing the break.
The old books mention this technique. In former times, CRTs cost several weeks' wages so there was nothing to lose. At the same time, shops that re-gunned tubes existed in some proliferation but have now disappeared. The last time I bought such a tube (colour) was back in 1982 from a one-man outfit in a former horse stable and it worked fine!
Thanks Bob for going through all the mess to do the electron gun autopsy, I know how messy that gets. My guess is someone "went for broke"; couldn't get any emission while trying to do a rejuvenation, so just kept increasing the filament voltage until the filament became a spark gap.
9:05 The wires in the glass seal are almost certainly Kovar, an alloy whose coefficient of thermal expansion is practically the same as that of glass. That prevents differential thermal expansion, which would eventually cause the seal to fail.
Neat little "forensic study" on that gun. Looks like that filament has a lot of hours on it. Undoubtedly the tube came from a high-hour set.
I am reminded of my careful extraction of all four wires from dual filament 12V bulbs to use in external grid triode experiments.
Great video Sir! It seems so important to document this kind of knowledge and information. Mesmerizing to witness. Thanks! - JRH
The end of the cathode gun is called a hermetic glass seal where the leads are sealed in by way of a melting process
that picture tube ended up looking like one that came through the post u.p.s 😊
Fascinating. Never seen a CRT filament before. I had just assumed it was a wire wound like a spring attached to two support wires, like an incandescent light filament. So is this wound more like a concentric cone shape to fit into the recess?
It's likely a heater for a hollow cathode cylinder. Only the face of the cathode needs to be hot, but that's a good way to get the heat over.
The construction would make more sense if it was taken more apart so you would see more of it!
Great video Bob!
Thank you great video and a great tip have a picture tube i can try that with i just tap the picture tube base and heater comes on
Very interesting, Bob. Way better than a photo or a line drawing in a book. How about a more in-depth tutorial on electron guns? Their constituent parts, why they were designed that way, and maybe open up the bell for a look at the screen? What technical problems had to be overcome during the development of the CRT? That would be super interesting. Think of all the views!
You are assuming I possess such knowledge ;) I know some stuff but not all the theory and history. Back of the screen is just white powder coating on the glass. Later CRTs had a thin aluminum layer over that to prevent ion burn.
That's a big subject. Search on youtube and elsewhere and bits and pieces can be found.
Light optics is the lens theory directly ported to electron rays. Identical. It is covered in detail in an RCA publication credited to Vladimir Zworykin called TELEVISION. Published around 1949 and widely available. Old theory textbook.
@@directcurrent5751 Yes, I have a copy.
There is always a risk with breaking the glass but the 'small' end should avoid implosion. I have shot these in the neck with an air-rifle and as a kid blasted a similar (non-safety mask) tube with a 'BB' gun. A little hole appeared on the inside and air rushed in as in your presentation. That said, I was told by someone of a garbage man being killed because someone left a TV tube in the domestic refuse. You cannot be too careful!
That was great Bob! Love that you took the investigation all the way. Did the phosphor get blown off the CRT face by the air rushing in?
Thanks. Yes. Just posted a photo on the community tab of my channel. Makes me wonder how that was avoided when CRTs were rebuilt?
@@bandersentv There was a video you could find on the ETF website where Hawkeye showed the process of re-building. One method used a tungsten bit in a Dremel that melted a small hole in the side of the neck by friction. The other method scored a line on the neck, covered it with tape, formed a crack under the tape by stressing the neck, then using a knife to cut a slit crosswise in the tape. Ha-ha! So obvious.
Yes, I added the link to the description.
Great content as usual Have you ever tried RF welding. I tried it once from an article in the UK Television magazine it used the output of the top cap of a valve line output stage to hopefully bridge the gap of the broken heater and re join it. When I tried it I'd did work but the heater only lasted for a few minutes after the process.
Interesting indeed. Thank you.
I really really wish i had Hawkeye's or RACS' rebuilding equipment in my garage because id dive right in and just do it. Shame theyre gone.
It's all at the museum.
@bandersentv yeeaaaahhhhh I've heard. I also have heard that it just sits there
@@bandersentv I wonder what happened to the RACs stuff. Is that also at the museum?
@@THEtechknight Correct. A dedicated room was built and all the equipment setup.
@@THEtechknight Some. The stuff that was practical to ship from France.
Such a shame that nobody picked up the trade of rebuilding CRTs after Hawkeye retired. :( there is still a huge need for it!
Money. Cost $300 to get a common 10BP4 rebuilt back in 2008. I'm sure it would cost even more now if anyone was doing it. Few would be willing to spend that much.
Lot’s expensive equipment and tooling needed along with skill. Sourcing raw materials like electron gun assemblies, cleaning chemicals, would be quite a task. Even with all that a high yield of good tubes would be difficult to achieve.
It would have to be a labor of love and deep pockets, not a money making adventure with such small volume.
@ebones6957 The early TV museum in Ohio has all the equipment and new gun assemblies. Problem is no one has the experience to operate it
@@bandersentvIt's a shame it's so difficult to make a living for most people that none of us seem to be able to take on the task and learn it at the museum.
One might be able, but lives too far from the museum. This stuff will be lost eventually. We'll keep it moving forward as long as we can.
Invite the younger people and treat them like gold. They will have to take care of this equipment and carry it and the passion into the future.
We tried 15 years ago. A large sum of money was raised to train folks at the last two rebuilders - Hawkeye in the US and RACS in France. Only one person stepped up and his situation has changed and is not able to work at the museum. All the equipment and new guns from Hawkeye is at the museum. I believe more guns from RACS were also shipped over.
I had success desoldering base pins on a WD-11 just as you have on this crt. I don’t like the idea of crimping the pins,tool or not. Once crimped it’s hard to uncrimp.
I never seen such a tool or seen one used. How did you recognize it when you found it?
I think I saw a picture of one before. Maybe in an ad
I did an experiment where i drilled a hole in a 12HK7 then i epoxide a fitting and connected it to my vacuum pump. Tube tested about 75% before and after increasing the heater to 16/17 volts it tested like 20%. My pump only goes down to 100 microns.
What kind of epoxy did you use? Ordinary epoxy may outgas and spoil your vacuum. There are special vacuum epoxies (and other vacuum adhesives).
100 microns is a very deep vacuum by even stringent HVAC standards. I've wondered how deep it could go.
Exposing the cathode to air may have poisoned it?
@johnnytacokleinschmidt515 Well, the vacuum pump was a cheap harbor freight one. There's ones that go down to 3 or 4 microns. Then connected to a turbo molecular pump. Then, the getter is heated inside of the tube. So i don't think I was close to pulling a strong enough vacuum.
I fixed an open filament on a b&w with a sencore once. Tap while hitting button method.
Just for the sake of it, could you turn a CRT into a funnel, possibly a sink?
Is it my imagination or does the filament wire get thinner as you approach the centre of the coil lengthwise? Could it be that it is a little hotter in the centre because heat conduct away at the ends more than the centre? If run at excessive temperature, perhaps the tungsten gradually evaporated off. This makes the wire a little thinner so it runs a little hotter and evaporates faster. A positive feedback loop that ends in failure.
Quite possibly. I wonder if it had a brightener on it? There also seems to be some sort of coating near the ends. Maybe to insulate against contact with the cathode.
A crt gun System from inside, cool.
Didn't seem to be much vacuum in that tube. All the ones I ever broke had a significant implosion.
It was a hard vacuum with shiny getters. How did you break them? Breaking the seal at the end of the neck is the safe way.
@@bandersentv Right. Any method that kills the vacuum through the thin glass. The thick areas of glass are thick because they are areas with high stress, break it there and there is too much force available. Like sticking a pin in a rubber balloon, it starts a tear that quickly grows because of the stress.
Shame it didn't work. Thanks for the tutorial.
Very cool!
I'm getting very exasperated with YT. I know they don't allow links in comments but apparently you cannot even mention the name of another YT author. That's very petty. I wrote a comment that indicated other videos on YT that showed the construction of CRTs and the comment has disappeared. Looks like YT is not interested in people learning more even if it is from another YT video author. A search on YT will turn them up anyway.
Sorry you're having trouble. Yes, they do allow links in comments. No idea why you are having trouble. If a comment has something they think might be a problem, it gets put into a pending approval area. Not sure what's going on here.
@@bandersentv Sorry about the mini-rant, but it has happened before so I just had to blow off steam. I probably need to get more sleep.