Repairing a damaged CRT/tube base
 

What do you guys use to secure a loose tube base ? I've used super glue in the past, but it doesn't seem to hold up well to heat. I did a little research and found an old phenyl glue recipe.

I wonder if Weldwood Plastic Resin would work :scratch2:

Here are some pictures of a CRT base I'm in the process of repairing. After removing the old base, I plan on attaching fine wires to the tips of the leads. Then, I'll thread them through the new base. I won't do that until I figure out the best glue to use though.

Here's the donor CRT base.
http://farm5.static.flickr.com/4118/...810a3b46_b.jpg

http://farm5.static.flickr.com/4098/...702e44ca_b.jpg

CRT gone to air, or are you out of CRT brighteners to use for bases?

As for glue, we always used DOW RTV3145 - gray silicone that is quite firm when it cures, and will allow things to shift when the temps cause expansion and contraction. The Navy uses RTV3145 on their Heads-Up Display CRTs. Good enough for A-7 Corsairs and F/A-18 Hornets, good enough for mid-20th century consumer electronics use.

Downside: Pricey.

Cheers,

Thanks for the tips. This was an oddball Westinghouse CRT I picked up from American Science and Surplus back in the mid 80's. It's a dud and I have no idea what it may have been used for.

Would epoxy putty work?

What's the original glue made from?

Maybe. I concerned about the long term stability with high temps. Here is RCA's old recipe from my earlier link. I don't think I'll find this in my local hardware store :scratch2:

This recipe for RCA's basing cement, yielding about 200 pounds of material, was "standard for all bases."

Coarse marble flour 170 lb.
Orange flake shellac 19-1/2 lb.
Durite phenolic resin LR275-2 7-1/2 lb.
Medium-color (grade G) rosin 3-1/4 lb.
Denatured alcohol 9 liters
Malachite Green aniline dye 10 g.

According to the Milliput website, their product stands up to 130 degrees C.

I can swing by the hardware store tomorrow and check out what the more generic stuff stands up to.

Hmm. I do know that a 6V6 I used super glue on broke down after a few days. That tube ran pretty darn hot. Over 130C I bet.

Anyone know the nominal operating temp of a CRT base of this type ?

130 degrees Centigrade is way more than the neck would ever experience. That's beyond the boiling point of water. I've used an IR thermometer (with tungsten filter to reduce the effects of the filaments temp) on CRT necks and found the temps to be about 140 - 180 degrees 60-84 degrees Celcius (~140 - 180 degrees Fahrenheit). That's probably why the Military used RTV rubber - withstands up to 225 degrees Celcius.

Cheers,

But they also farm out EVERYTHING ot the lowest bidder. Anyone who's ever had the (dis)pleasure of working on the F/A=18E/F anti-skid braking system will tell you what a POS it is, so I'm not inclined to believe Military technology is necessarily the best out there after what I've seen. That said, I do like RTV for a job like this. I've personally had good luck with Wacky Glue, the base of the CRT in my Halolight is still stuck on prett hard.

I was tempted to mix up the base recipe also. Finding the Durite Phenolic resin turned out to be too difficult.

Scotty says he uses a silicone RTV.

It works. But, it makes me just a little nervous when I plug on the socket. It tends to flex which must put a little stress on the leads.

If you use a one part RTV try to find one that doesn't make acetic acid during the cure.

John

Thanks for the tips. I'll swing by Menards tomorrow and see what they have.

Speaking of silicone, I've used Permatex Windshield Sealer for a varety of things. It doesn't give off that stinky acidic smell but it is quite flowable so do allow it time to cure. It's also clear. I've used it on flybacks with good results.

It will harden up better than regular RTV, kinda' like a hot glue stick does when dry. You can pour some out on a piece of paper or whatever, let it cure overnight and see if you like the results before using it on your socket.

"Temperature range -80°F to 450°F" - that aught to do it :D

Someone once suggested furnace cement, but I've never tried it myself.

RTV3145 does all of that - it cures fairly firm - softer than hard rubber, but firmer than your typical silicone sealant. And the US Gov't spec for all silicone products restricts the % of acetic acid (actually acetyls). The stuff is pretty stable in the tube if unopened - the reason I mention that is someone on fleabay has some (recently) expired tubes. Shelf life for the stuff is two years, so it get's surplused pretty often. New tube of the RTV3145 goes for 23-28 bucks, so "cry once" as they say. The stuff is available online everywhere. Use masking tape for potting the stuff. You can't speed cure any RTV (room temperature vulcanizing) Silicone. Skins in about an hour or so, and you can handle it in 24hrs. Cleanup of any extra is easy - I use an Xacto knife - we used surgical scalpels in the Navy - but a razor blade works as well.



Cheers,

Yeah, the Anti-skid system, the servocylinders, and the AAS-38 FLIR all were POS. Saw plenty of them broken in both peace and wartime ops - a VFA "up" status meant it could fly a minimal tanker sortie - "Really up" and they would actually fly ordnance! Semper Tomcat!

As far as the RTV, DOW and GE make great RTV products - it's the come-later companies that you have to watch out for.

Cheers,

I used epoxy...
 

I used ordinary two-part epoxy on the loose base of an 0D3 voltage regulator tube in a Hallicrafters SX-71 about fifteen years ago. This tube runs really hot but it's still solid.

Harry
Maryville, Tennessee

Actually the servos never really gave us much trouble, it was the skid control box. It's analog when it needs to be digital, to do sampling and all that jazz. As for the FLIR- when it was up, it stayed that way all cruise. If it went down, you never saw it again. :tears:


Maybe for the Legacy jets, our Supers were rarely in that category. In fact on my last outing with 154, we flew more in country hours than all the others COMBINED. Even dropped a pair of 1000 pounders on our last run. :thmbsp:

You're right - I just now noticed the E/F - saw them only with the Test Wing at Pax River - 90% were project birds and couldn't go the AIMD route for parts. Of those few others, we got only a handful of parts - the rest went to Oceana or depot.

All of my time with Hornets was with A and C birds - 4 deployments - Navy with the Cs and the Marines with the As. They were our number one customers. Same CAG for 3 of the deployments, and one VFA outfit was worst on all three. Sucketh maximus.

Cheers,

The operation appears to be a success :banana:

Old base removed.
http://farm5.static.flickr.com/4107/...d7d3ed9d66.jpg

I soldered fine extension wires to the tips of the CRT wires. That makes it a lot easier to thread through the new base pins.
http://farm5.static.flickr.com/4146/...47dbab380a.jpg

I found some Permatex RTV in the garage so that's what I used. The old resin cement is mostly intact and in good shape so I left it alone. That meant I really didn't need to use much glue after all. It's only been an hour but it's holding well. I'll know for sure in 24 hrs after it fully cures.
http://farm5.static.flickr.com/4106/...092d1acc79.jpg

Most importantly, it still test good :)
http://farm5.static.flickr.com/4154/...4b50f1f837.jpg

Cool LED flashlight/lantern! Where'd you get that neato item ??


Cheers,

Thanks - it comes in very handy. Especially when working out on the back porch at night!

Can't remember exactly - either Home Depot or Menards. I got both the lantern and mag light in a combo pack for a couple bucks. They're still running bright on the original batteries after 8 months. My only complaint is that they take AAA instead of AA. I've got loads of AAs lying around.

I just got a rebuilt tube back from Hawkeye. Scotty did use a white RTV of some sort. There's definitely a little play in it, but not so much that I'm worried about the wires breaking.