C3g tubes

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C3g tubes

Postby mordy » Wed Nov 19, 2014 3:50 pm

I am a member of a group exploring the use of Siemens C3g tubes as driver tubes in tube amps. At least four of us have experienced breakage of these expensive tubes, even when handled very carefully.

Is it possible that these tubes are very fragile, or is there some kind of design flaw that does not allow normal tube rolling (wiggling) of the tube to remove it or put it in?

It seems very strange that such an experienced company would make such an expensive tube so fragile.
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Re: C3g tubes

Postby Jac » Thu Dec 18, 2014 10:29 pm

This tube was produced 20 years or more, in large quantities.

So you didn't discover a problem with the tubes. Rather you are doing something wrong.

When you write breakage, I suppose you mean glass breakage. Did you remove the metal can? Then you should be relatively safe.

Anyway when you wiggle the tubes out, you need to be careful not to bend the pins. Try to pull it out, nicely as vertical as you can. If that doesn't work, dont get angry, and wiggle with violence! No tube will like bended pins, and glass cracks along the pins can occur. Some Chinese sockets have a too stiff center pin. You may change the shape of that a little bit so it becomes less stiff. Or better use Yamamoto sockets, or NOS sockets.
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Re: C3g tubes

Postby mordy » Fri Dec 26, 2014 1:36 am

Thanks for your reply and your advice. I have rolled hundreds of tubes without cracking the glass envelope, not even once. Since these tubes were made for transatlantic telephone communications I assume that they were made for underwater installations. Is it possible that the glass was tempered to withstand the underwater pressure and thus the glass would be more fragile than other tubes?

I have widened the socket holes and the center hole. In addition, I stick a small flatblade screwdriver between the socket and the metal tube bottom and gently lift up the tube with incremental movements.

I did take off the metal envelope from my broken tube but found it difficult to do.
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Re: C3g tubes

Postby Jac » Tue Jun 16, 2015 5:26 pm

I think you just cracked one of the pins, and air got in.
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