Broken Index Pin on Octgal tube bases--best mending adhesive?

[nevetslab]

In the last Ampeg SVT-VR repair, where the power transformer had no mounting hardware to keep it in place, it only got as far as moving onto V3 6550 power tube location, breaking the center index pin on the tube base.

In the past, I've had little to no luck in getting the recovered indexing center pin to bond, without it just breaking off again at the glued joint. This one I tried some Loctite GO2 gel on both joint surfaces, let that sit for 30 sec, then put the center pin back into place and held it under finger pressure for 5 minutes before removing my fingers. Of course, the stupid pin moved, so I had to re-position it again, then carefully set it into a coffee cup to set up for a day.

It did remain on the tube base while I went thru and checked all the tubes in that most recent SVT-VR repair, and I was lucky to not have the pin break off during installation or removal.

What ave you guys found to be the best adhesive for repairing these when they break off?

[mac dillard]

Mark the location of the index pin with a permanent marker so you can install it correctly and forget about the pin....If you intend to use the tube.

[nsubulysses]

what's nice about when the middle index breaks off is it usually fits right back into the the rest of the base perfectly where it broke off.

I have broken the middle index off my bias probe and just used basic gorilla glue and a clamp. It lasted probably a year of in and out before it broke off again. A tube will never come in and out of the socket as much as a bias probe. I let it dry overnight.

[Gregg]

Don't bother gluing the pin. Just put a tiny strip of sicky paper or similar between pins 1 and 8 at the outside of the base and that's it or mark it with permanent marker as already suggested.

[Enzo]

I would NEVER do that. I might use the index mark, but the guy who owns the amp won't. First time that tube leaves teh socket, I will bet my lunch money it goes back in the hole wrong.

There is a commercial product:
https://www.tubesandmore.com/product...ce-octal-tubes

[nevetslab]

Ah...I hadn't seen those for a long time and forgot all about them. After scaling the drawing with calipers, it looks like the base is 1/16" thick. So, very little impact on the tubes' pin penetration into mating sockets. Good suggestion !!

[Axtman]

I have broken or had tubes with broken index pins. As much as I hate to do it, I throw out the tube and get another one. I have tried various super glues and epoxies with no luck.

[mozz]

There is a commercial product:
https://www.tubesandmore.com/product...ce-octal-tubes

Cheaper here.
https://reverb.com/marketplace?query=octal%20repair

[drewl]

Well I'd show the customer how to install the marked tube.

I'm a little leery of using flammable epoxy in on an item that gets hot or is near potential sparks.

[Leo_Gnardo]

I'm a little leery of using flammable epoxy in on an item that gets hot or is near potential sparks.

I've used JB Weld fast setting (5 minute) epoxy lots of times, never a problem, doesn't catch fire. One epoxy tube may be marked "steel" but that's baloney, it's just salesmanship, there's nothing conductive in it. I'd be much more leery of someone plugging in a keyless octal tube in any of the 7 alternate ways it won't work.

[g1]

Another vote for JB Weld.

[Justin Thomas]

I'd be much more leery of someone plugging in a keyless octal tube in any of the 7 alternate ways it won't work.

Fiend of mine's first tube amp was an old used 100W Peavey head. He took all the tubes out to clean it up, Put them back in, fired it up... I won't forget the phone call: "hey, one of my tubes is lighting up like a light bulb." "Okay, that's normal..." "No, I mean, like a 100W light bulb!" "TURN IT OFF! TURN IT OFF!!! I'll be right over!"

Luckily, he only killed the tube. We got him a new quad with good base pins and he was rocking out.

Justin

[Enzo]

I don't care how many people you show the way to insert the un-keyed tube, there will always be plenty more people, and we are just asking for the tube to be shoved in wrong when there is nothing to stop it.

Pins 2 and 7 are essentially shorted together within the tube. Normally they handle the heater current. But let's move them around.

3 to 8 - shorts B+ to ground
4 to 1 - shorts screen node to ground
5 to 2 - shorts bias to heater circuit
6 to 3 - shorts B+ to screen node in many Fenders
7 to 4 - shorts screen node to heater circuit
8 to 5 - shorts bias to ground
1 to 6 - shorts screen node to ground in many Fenders.

[Axtman]

My experience with JB Weld to reattach a broken index pin was that it did not hold very long. That said you can always try it after all the tube is already broken. Be sure to wipe the excess off the outside of the pin since a glob may prevent you from inserting the tube in the socket.

[TimmyP1955]

I've broken a number of BiasRite pins. Superglue holds for at least a handful of insertions and removals. Seems to be the same plastic as used for tube bases.