2. misc-audio
  3. 1244756431

How do you remove a tube Key?


I’ve had this issue before but it was during a DIY tweak to the amps so I could bias them by myself. The amps were both opened up by a friend and it was simple for him to do the fix.

EL 34 tubes have what I call a locator key. The plastic part down by the pins that locates the proper alignment of the tubes into the tube socket. It also covers the point where the glass tube is drawn out, providing protection to that slim glass point amongst the tube’s metal pins.

Thinking to rotate some of my tubes from one amp to the other, the tube came out but the plastic pin/key stayed in the amp. Super.

Consequently another tube couldn’t be interchanged with that spot until the plastic piece is removed.

Is there some way to remove this piece without opening up the amp and pushing it out from behind the tube socket itself?

Also, What about re-afixing the plastic thingy to the tube itself?

Don’t worry about that, or what?

BTW… as this has happened to me at least once before, is this a common thing?

Can it be overcome/avoided somehow, apart from the obvious… don’t mess with it once they are in place bit… ? Or is this just part of using EL 34 based amps?

Mucho gras'
blindjim
7 responses Add your response
blindjim OP
3,092 posts
 

Thanks much.

Good ideas all.. especially Rod's.

I can't tell really if things got broken off... I suspect the glue just came free between the glass and the plastic cup covering the nipple of the tube.

Likely heat and cooling, etc... and or poor QA. beats me... they're Russian 34's, and were bought new from AES, in AZ.

BTW... FWIW 2, rotating a couple of the tubes from one block to the other, and repositioning the preamps power sup was worth the effort... suprisingly so!

This deal never ceases to amaze me how apparently minor changes can affect such noticeable results.

THX !!
dopogue
1,773 posts
 
You apparently have another problem that hasn't been mentioned -- the tube fitting way too tightly (the key part anyway) into the tube socket. When a key has broken off for me, the the broken-off part has come out very easily -- just insert anything pointed and pull it out. If there is any resistance at all I'd think you need one or more new tube sockets. Just for what it's worth. Dave
thorman
1,262 posts
 
I did have one recently and once the amp cooled off I used a small piece of duct tape and stuck it to the pin and it came out very easily...
rodman99999
6,159 posts
 
Find a long sheetmetal or wood screw, large enough to grip the inside of the locator's hole, partially screw it in(just enough to bite) and use it to pull the piece out.
elevick
2,636 posts
 
Most people learn the hard way to remove tubes by the bases only. I wouldn't try to put a tube back together. Do it wrong and you could fry a lot more stuff.
ghostrider45
449 posts
 
Make sure you're insulated, the amp is unplugged, and the filter capacitors are discharged before using a tool to remove the key. Otherwise you might get a surprise if your metal tool accidentally comes into contact with the plate or screen grid pins in the tube socket!
jax2
3,031 posts
 
I've had that happen once with an NOS tube, Jim. You can glue it back on with some two part JB Weld and it should be as good as new. Obviously take care to put it back exactly as it was so the key orients the pins properly. It certainly makes getting the orientation easier, but does not have to be there to do so if you are careful. You could try using a pointy L-shaped dental tool to get some purchase on the interior of the piece and pull it up slightly. I think you can find similar tools at a hardware store or hobby shop (don't use these for your home dental practice though). Once it breaches the edge of the socket you can grab it with a pair of needle nose pliers. You could also search out some kind of expanding bolt fastener for attaching things to drywall. There's probably one that would do the trick, though I'm not positive. Insert the expanding end and hold it with a pair of pliers while you screw the bolt down to expand it. Once expanded pull the bolt upwards. It may be a tricky thing to get out once expanded, but I bet a bit of twisting ought to do it.

Good luck.
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