• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Maybe a Ruskie

I got an interesting (to me anyway) miniature (9pin) tube by accident. In a shipment of Chinese 12AX7Bs One tube looked a bit different.

It is about half again as long as the 12AXs and has a structure that looks like two rain gutter sections put top to top and fused together with the octagonal insulating waffers closing off the top and bottom ends. I don't have enough experience to tell if it is the plate or some kind of shield.

On a little wire above the structure just at the point where the envelope sweeps in toward the evacuation "nipple" on top is a structure that looks exactly like the little halo that J.R. wore with his angel costume in the Christmas play.;) This is no doubt to impart that sweet angelic tube sound.

The writing on the envelope is a bit hard to read with the second character of the first line being somewhat suspect. It looks like it says.

6P14
70.4

but it could be something like 6814. I purposely did not look at any data sheet databases until I had written down what I thought it said because I didn't want to be influenced by what I expected to see.

I will get access to a didcam on about thurs and will post pics but judging by the description is 6P14 a likely candidate? Other possibilities?

mike
 
Your point is indeed valid Wavebourne. In fact I got this stash of Chinese tubes for the developement stage in part so that if I fry tubes buy my ineptitude they will be $3 tubes instead of $15 tubes. After the design and testing are complete I will order up a complete set of quality tubes such as JJ and/or EH. Then some of the Sino-Glass can be used as spares.

mike
 

tubewade

Member
2007-06-03 8:54 pm
It holds/held the material called the "getter", which is used as an aid during the evacuation process. It is responsible for the mirror-like appearance on the glass on the top of the valve. The same technique is used in practically all valves, not just 6BQ5s. This material oxidises with the presence of oxygen so if you ever find one that looks white and flaky rather than shiny, the envelope is leaking and the valve is no good.