Help, I broke a tube

[Misanthrope189]

Hey,
I just got some new tubes for my Mesa 50/50; JJs 6L6s. I was trying forever to get this one power tube to go in, and no matter what, after the other 3 went in smoothly, it felt like this one kept getting jammed. So I would pull it out, and try again, moving the tube around in a circle to try to let the prongs slip in the right slots. Unfortunately, one try I was pulling the tube back out, and the plastic prong in the middle, the big fat one, not the metal ones, broke off. Being it was a hollowed out plastic prong, I figured it didn't really serve a purpose but for stabilization, and now finally got the tube in. However it doesn't work now (the tube doesn't light up) and I figure I need to send it back, buy another one, or try to replace it...but in the mean time, I was wondering what the plastic prong actually does, if it breaking is what caused the tube to quit.

Thanks,
Nick

[Overlord]

Re: Help, I broke a tube

I don't remember what the proper term for the plastic prong is anymore, but it has a couple of uses. It covers and protects the pointed end/tip of the glass tube that was left during the manufacturing process. If this tip is broken, the tube loses the vacuum. Usually the plastic prong is keyed so that they only fits in the socket one way. I have an old Fender amp that would wiggle the tubes loose and ultimately they would fall out. Both of the prongs have broken on these tubes, but they still work since the glass is intact. The first thing I would do is check the tube that you originally removed from the amp to insure the prong is intact, if it broke off, it may still be in the amp. This would cause problems installing a new tube. Then check to see if the tip under the broken prong is still intact on your new tube, if it isn't, the tube is ruined. If it is still intact, check to see if the prong was keyed originally and make sure it is being installed with the correct orientation. I am not familiar with 6L6 tubes, so I don't know if they are keyed by the pin pattern or the prong.

[Misanthrope189]

Re: Help, I broke a tube

Well, I didn't break the glass on the tube, so why doesn't it light up or get hot? Maybe it's a fracture I can't see?

[charvelguy]

Re: Help, I broke a tube

Those are octal sockets. The plastic part has the notch that serves the purpose to ensure that the tube is lining up to work within its proper position.
If the glass tip wasn't broken, then the tube should still work. Did you pull the broke off portion out?
Usually, you can glue those back on with super glue and if you are gentle the fixed break will hold.

You have to be sure the tube goes in properly with the notch in the correct position. Make sure the pins aren't bent (metal prongs) They have straighteners for these.. but you can use a needlenose pliers and eyeball it in a pinch.

[Misanthrope189]

Re: Help, I broke a tube

Alright, thanks...I'll try it again, hopefully it'll work.