17LP4 CRT ( Need one... ) - Page 2 - Videokarma.org TV - Video

RitchieMars · #16 07-19-2010, 05:51 PM

Hey, that tube might be just what I'm looking for! Let me know how it tests when you get around to it. If it's good, maybe we can work something out. @ grimer

Yeah, I don't think I have a way to apply voltage to my tube other than plugging it into my television. Or well... there is another possibility... but anyways, I read very little resistance across the heater pins, very low at first and then it fluctuated and came back to about 1 ohm or so. I guess I'll leave it be and see about getting the capacitors in order. Looks like I can get them all for about $40 from JustRadios.

rojoknox · #17 07-19-2010, 06:19 PM

Greetings from FixitLand!

Quote:

Originally Posted by RitchieMars

What do you guys know about the interchangeability of CRT's? The one in my television was originally a 17LP4 and/or 17VP4. Are there any other compatible 17-inch CRT's that might interchange? If so, I'll have to keep a look-out for those also. So far, I've read about a couple different variations made during this period that are very similar to the 17LP4. The main difference I've noticed is that my CRT is uses an electrostatic focus, and many of the other types are magnetic. However, the 17RP4/17HP4 has nearly identical specifications to the 17LP4, and also uses an electrostatic focus.

The 17LP4 and 17VP4 have a cylindrical faceplate; that is, it curves from left to right (which you can see looking straight down its face) but vertically it is flat (which you can see looking across its face). (Sony Trinitrons were made the same way.) The 17HP4/17RP4 faceplate apparently curves both horizontally and vertically, as most tubes of that era do. So, electrically it may be quite similar, and actually work, but mechanically it will probably not fit the TV's picture mask properly.

My 1952 Zenith K1846R also uses a 17LP4 tube. So did my first set, a '53 Motorola TV-radio-phono unit.

Take care,
--
J. E. Knox 'The Victor Freak'

John Marinello · #18 07-19-2010, 06:37 PM

I had a 21fjp22 that did that, under the blue lateral magnet. Symptom was a dim picture. I cleaned off the neck, put some silicone around it. I turned the set on and left the house for ~4 hours, came back, fixed... pic was back to normal. No problem.

leadlike · #19 07-19-2010, 07:50 PM

that's what I did to the cracked 10fp4-spread silicone over the cracks, and wrapped it tight in electrical tape. I could see how getting it sealed and running the filament would get the few air molecules moving enough to be gathered up by the getter-if there is any of it left.

Potentially you could have a perfectly good cathode still. The crack may have gotten onto your tube when someone carelessly bumped the back of the set against the wall, since the tip of the neck tends to stick out of the backs of many sets. Don't ask if this has happened to any of us!

RitchieMars · #20 07-19-2010, 07:54 PM

Hm, I had been thinking to myself that maybe there was a way to seal the crack. But... I was under the impression that losing the vacuum ruins the tube and there was no way to get that vacuum back once air got in there.

So uh, I could seal my crack with silicone and run the set for awhile and see if that helps? Hm, since I don't have any way of running my filament other than the tv itself ( that I'm aware of ) I guess this is something I'll have to try once I get all my caps replaced.

jeyurkon · #21 07-20-2010, 06:59 AM

Quote:

Originally Posted by RitchieMars

Hm, I had been thinking to myself that maybe there was a way to seal the crack. But... I was under the impression that losing the vacuum ruins the tube and there was no way to get that vacuum back once air got in there.

So uh, I could seal my crack with silicone and run the set for awhile and see if that helps? Hm, since I don't have any way of running my filament other than the tv itself ( that I'm aware of ) I guess this is something I'll have to try once I get all my caps replaced.

You don't have anything to lose. However, silicone RTV is quite permeable to oxygen so it doesn't provide much of a seal.

http://www.silicones-science.com/grades_elastomers.html

John

leadlike · #22 07-20-2010, 07:51 AM

Well, if luck is on this tube's side-would just putting something over the crack be of benefit? After all, the leak is rather small, so the perceived pressure gradient may not be too extreme. Are there any other relatively available materials out there that are relatively impermeable to the atmosphere but still effectively bond to glass?

Phil Nelson · #23 07-20-2010, 08:55 AM

If grimer has a good tube for you, that seems better all around than trying to seal a big crack.

There is an expensive product called Vacseal. Some folks apply it on the leak-prone parts of 15GP22 tubes on the theory that it can't hurt and might help prevent future leaks.

http://www.2spi.com/catalog/vac/vacleak.shtml

Even if you seal that crack, I'd be concerned that heating & cooling during normal operation could make the whole thing go PLINK at any time. Once a crack starts, the weakness may put stresses on the rest of the neck.

Phil Nelson

John Marinello · #24 07-20-2010, 09:42 AM

I used RTV-1. It worked fine for 2 years until the fly failed. The set was then pitched.

***Eric H*** · #25 07-20-2010, 10:52 AM

The Getter is white, this tube has gone to air, it's done.

The only thing now it to look for a replacement, they do pop up now and then you just have to keep looking.

jeyurkon · #26 07-20-2010, 01:45 PM

Quote:

Originally Posted by leadlike

Well, if luck is on this tube's side-would just putting something over the crack be of benefit? After all, the leak is rather small, so the perceived pressure gradient may not be too extreme. Are there any other relatively available materials out there that are relatively impermeable to the atmosphere but still effectively bond to glass?

Someone pointed out Epotek 353ND to me. It provides a nearly hermetic seal.

Quote:

Originally Posted by Eric H

The Getter is white, this tube has gone to air, it's done.

The only thing now it to look for a replacement, they do pop up now and then you just have to keep looking.

I'm inclined to agree with Eric.

It may have had a small crack to begin with, but under the stress of handling suddenly got much worse as Phil suggests.

I once tried to make a vacuum chamber by sealing pieces, that were assembled in the shape of a soccer ball, with RTV. We wanted to use a flexible material that wouldn't crack. We were unable to achieve a very good vacuum because of the permeability. We ended up overcoating the RTV with an epoxy.

John

grimer · #27 07-22-2010, 08:41 PM

BAd news,this tube I have here shows no sign of life at all,the filament lights up but no emission,even at 8 volts

But I suppose it was worth a try
Pat

***Eric H*** · #28 07-22-2010, 08:44 PM

Quote:

Originally Posted by grimer

BAd news,this tube I have here shows no sign of life at all

But I suppose it was worth a try
Pat

Is the heater lit?

Possibly re soldering the pins would help?

grimer · #29 07-22-2010, 08:51 PM

Yup,the filament lites up.I let the tube warm up for 20 minutes,even cranking
up the heater to 8 volts did not help.

bandersen · #30 07-22-2010, 09:04 PM

I had the same problem with a 16KP4 recently - good filament, but 0 emmision. It turned out to be an open cathode. I was able to re-weld it by using the technqiue described over here: http://www.videokarma.org/showthread.php?t=248067
Just a thought.