Rethreading a CRT Questions
 

I picked up an Admiral 30A1 S-F with a 10" CRT. The CRT tube is detached from the socket, but there are lengths of wire left, so I will be attempting my 1st redo with this type of thing.

I found a couple good posts of how-to-do's, but it was a little vague on exactly what brand and type of glue to use? So that is one of my questions. Another is just how much glue to put on the inside of the socket, and whether to put any on the outside?

I read when soldering a new long lead on, to just lay the new lead alongside the old lead after tinning them, and solder them together. Correct? Wont that remelt when I solder the new leads at the end of the socket? Or is that a super quick hit with the solder iron?

I dont know if the tube is good or not yet, but I thought this would be a good thing for a rookie to do for practice even if it is junk. I'll test it if I get this done without breaking a wire. THANKS!

I use new leads that are much thinner and coil one around the end of the old wire...I think it is more secure that way.

Glue I can't recommend any. I've tried super glue and it just comes loose. I've tried hi-temp silicone but not ran that tube enough to confirm hold....If a Base is still on a tube and the glue fails I just wrap the joint with electrical tape, and that seems to hold okay.

BTW the half of the connector that is normally part of a tube is called the 'Base' the half that is part of the chassis that the tube plugs into is called the 'Socket'. Correct nomenclature reduces confusion. :)

Yes, it will remelt. That's the point, the extension wire is just temporary to help thread the old lead into the hollow base pin. It's meant to be removed.

Now that's all assuming the old leads coming out of the CRT are intact and long enough to extend down into the base all the way to the tip of the base pin. If they've broken off or been clipped, you'll need to attach permanent extension wires.

I use Permatex Flowable Silicone Windshield and Glass Sealer

https://www.farmandfleet.com/product...ss-sealer.html

Thanks guys! My wires are still full length, at least until I get started messing with them. Ive used that type of silicone before. Sorry for my improper terminology. I know better on that one.

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Vacseal was mentioned at the end of this link that I found, but Im not sure thats it. Its priced way over my budget for a single application. http://www.videokarma.org/showthread.php?t=76553

Silicone should be fine to glue the plug back on. Automotive urethane if you want it to never come off (kindof overkill).

The old base compound recipe is near the end of this article... might want to reduce the proportions somewhat.

http://www.antiquewireless.org/uploa...acuum_tube.pdf

jr

If your wires are still full length, they shouldn't need any extensions. Just carefully aim them back into the plug making sure that each pin is clear. Tinning the wires or at least (very gently) cleaning them up will help. Then heat each pin until the solder wicks into the plug pin hole. I've always played exactly how much solder to use by ear and came out fine, but I wouldn't be to conservative or you may not get a solid connection.

Good luck!

I was thinking of this myself, if they are long enough. I'll play it by ear when the day comes, after everything is cleaned up well. i think Im down to 2 other small projects first, one being a Blonder Tongue install which Im very excited about, the other to piece together a radio project.

I don't have much direct experience of gluing the bases back on to tubes but the received wisdom here in the UK is to avoid superglue (cyanoacylate). Apparently it can cause the glass to crack. The usual suggestion here is Araldite (2 part epoxy resin).

I wonder if superglue cracks the glass because it gets hot sometimes. Most epoxy glues are also exothermic, but I don't think to the point of thermally shocking the glass. Then again I did use a Permatex epoxy glue once that literally burned me while using it.

I think the problem with superglue is that its coffeicient of expansion is very different to glass so when the tube gets hot it causes stress. Araldite is relativel soft when fully cured so allows for some movement.

I glued on two bases this weekend, using flowable silicone like Bob Anderson recommended also in a previous thread. http://www.videokarma.org/showthread.php?t=267995

See attached picture of the silicone tube with pierced end - a 1/16" bit drilled from inside out. To mate with the nozzle, a very carefully dremel-drilled 9/64" hole in the BLANK pin 8 and 10 positions of base was the injection point.

CRT is face-down during process, curing in 24 hours. It was tight this AM. I did one of them warm, just off the CRT tester. The other at basement temp. Will see which holds.

Half a tube was used on each base in one hole and it flowed in and around the base closest to the CRT glass. Most or all of the wires going into the CRT may be covered also. Looking into the second hole, it was showing a rising level of silicone.

CRTs were both RCA 21FJ color roundies and bases were just loose enough to risk lead wire fatigue when socket is pushed on-pulled off. Oddly enough, no silicone flowed out where base meets glass on either one. Once solid, another test then re-flow solder into the pins to finish.

I hope you never need to get those bases off. I do it with the CRT face up and just run a bead along the base. It really doesn't take much to hold it firm.