17LP4 CRT ( Need one... )

[jeyurkon]

Those are pretty impressive cracks. It's difficult to imagine that the tube hasn't gone up to air, but yet you say you still get a dim picture.

What does the getter flash look like? Is it still shiny?

Rebuilding is expensive and if you can get an NOS one, then if this one works well enough to keep you busy restoring the set, then I suppose it makes sense to use it until you find one.

John

[marty59]

Just my opinion on your tube...I'd agree about trying to find another one. Even if you shipped the one you have (cracked) the handling and shipping of something that is just more fragile may not make the trip.

[RitchieMars]

If the "getter flash" is what I think it is, it's shiny. All of the visible parts of the beam gun look almost like chrome, aside from these 3 transparent cylinder things.

The light I could see coming from the neck of the tube when it was in operation was fairly decent, brighter than any of the other tubes. At night in a dark room, I could adjust the ion trap to get a full raster, bright enough to cast a glow a few feet from the tv. Turn on the lights, and it's practically nothing. I was able to get something of picture, at one point ( in the dark, of course ) although the images flipped and scrolled, and went slanted into chaos. Aside from this, I've also never gotten any sound other than a very small crackle from the speakers and I only heard this once or twice as the tv warmed up.

With the dim picture, I'd assumed that the CRT was bad all along but I didn't know about the crack until now. But, I also knew it needed caps and probably a couple tubes so it hasn't been turned on for months. Right now it's been taken apart ( there was no spark when I discharged the CRT ) and it's got a nice, clean chassis after I went through it last night and this morning.

I've already located a company that sells new 17LP4's, but it would cost $185. It would be oh, so very nice if I found one a bit more affordably than that. For now, I'll get my schematics, recap it, and test it with what I've got. I'll just pay attention to my CRT when it's running and see if it smells like ozone near the back...

[jr_tech]

Originally Posted by RitchieMars

If the "getter flash" is what I think it is, it's shiny. All of the visible parts of the beam gun look almost like chrome, aside from these 3 transparent cylinder things.

Just for grins, I have posted a picture of a CRT getter flash... It is an evaporated coating of barium deposited on the inside wall of the glass, to "pump" residual gas after the CRT is sealed. In this tube, the gun parts also look fairly shiny, but that is not what you are looking for... the getter flash is visible through a small rectangular window in the gray dag coating. It is shiny, and in this tube, exhibits some "rainbow" color around the edge.
Note: this tube uses cream colored ceramic supports for the gun elements, rather than the clear glass support rods seen in your CRT.
jr

[RitchieMars]

Hmmm... in light of this information; is my getter flash still shiny? Eh... not so much...

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.

Here's the specs for the 17LP4:
http://www.shinjo.info/frank/sheets/137/1/17LP4.pdf

Oh, and below is my not-so-shiny getter flash.

[grimer]

I have a 17lp4 that I do not need,it is stored in a plastic bin behind my garage.
Probably be able to get it out and test it this weekend
Pat

[leadlike]

Look at your getter, it looks like it has been "got".

[jr_tech]

If you don't have a crt tester, there is an easy way to determine if the tube is very gassy. IT IS A DESTRUCTIVE TEST IF THE TUBE IS VERY GASSY!

1. measure the heater resistance... should be fairly low, like a few ohms.
2. apply 6.3 volts to the heater (Pins 1 & 12)... does it light up normal brightness? if so, the CRT may have a decent vacuum in spite of the crack and "used up" looking getter.
3. if it just barely lights up, it will likely burn out very quickly, perhaps you will see a flash. Tube is very gassy and now has a burned out heater.
4. re-measure the heater resistance... if the tube is very gassy, it is now likely "open".

Here is what happens...the heater resistance is much lower when it is cold than when it is hot. If the tube is gassy, air molecules will transfer heat away from the heater, so it will remain fairly cold. Since the heater resistance stays low, it will draw more current than it is rated for, and open up like a fuse.
Even if the tube is very gassy, continue to handle it carefully, as it still could have a partial vacuum, and be an implosion hazard.
jr

[RitchieMars]

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]

Greetings from FixitLand!

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'