[vwap]

I've been getting into tubes lately, and had a few questions on some of the tube 'lingo'.. so if any of you tube gurus out there could help..

Like:

What exactly are 'triple mica' spacers? (Perhaps pictures illustrating them would be helpful?

)

A lot of tubes, especially tubes used in audio, have letters affixed after their number.. what do those modifiers do? (If anything).. Like: 12AU7A/WA vs 12AU7 or 6SN7GTA/GTB/WTA vs. 6SN7.. etc?

What's a ribbedplate as opposed to a smoothplate? (I think this would be self explanatory if I saw some tubes that were ribbed vs. smooth)

Yeah.. I think that's it for now..

 

[braillediver]

A Telefunken 12AX7 smoothplate.

Triple Mica

Windmill getter

Mitch

 

[vwap]

Quote:

Originally posted by braillediver Triple Mica

Hmm.. so with the triple micas, it seems there are two plates stuck together, and another raised above on supports?

 

[ServinginEcuador]

To give an explanation about nomenclature, here's the long and the short of it:

Each series of tubes start with one in the family, for example 6DJ8. It was a tube that lasted 2500 hours before going bad. Later on they came up with a longer lasting tube, 5000 hours, and called it a 6922. Still the same pins, same voltages, but of a different construction or better materials to make it last longer. Last they came up with the super long life tubes lasting 10000 hours. These were called 7308 tubes.

I think the same applies to other series of tubes. Sometimes it can mean the same tube, but a design change to accept higher voltages than the original. I believe the 6SN7GTA/GTB tubes were different due to the ability of the B series accepting higher plate voltages.

 

[vwap]

Quote:

Originally posted by ServinginEcuador I think the same applies to other series of tubes. Sometimes it can mean the same tube, but a design change to accept higher voltages than the original. I believe the 6SN7GTA/GTB tubes were different due to the ability of the B series accepting higher plate voltages.

Ahh.. yes. I remember reading that somewhere.. the diff. between the 6SN7 tubes..

Another question.. how might the different ratings affect the test results, especially on the TV-7, where sometimes they don't have test settings for some of the 'modifier' tubes.. (For instance, the 6SN7 only has settings for the 6SN7, but nothing else..)

Should I test them with the same settings?

Thanks!

 

[mkmelt]

Duncanamps.com, under the technical page, under tubes, is the best page I have found that explains what all of those mysterious numbers and letters mean.

http://duncanamps.com/technical/tubenumber.html

To answer your specific question:

Additional tube letter designations defined:
A - Controlled heater warmup time, although can also be used to denote increased ratings or performance over and above the non-A model.
B - Improved ratings/performance.
C - Ditto.
G - Glass bulb.
GT - Glass tubular.
W - Ruggedised version.
X - Low loss ceramic base.
Y - Low loss phenolic base.

 

[vwap]

Ah.. another question. When I'm testing a:

5727 tube, I'm supposed to hit "4", or "GAS1" (on my TV-7). What exactly is it testing for? Is it transconductance (I'm feeling that it isn't..), or gas content or what? (5727 is a Gas Thyratron tube)

or

rectifier tube of some sort (like an 6CA4 or an 83 or some such)... When I hit the rectifier test button, what exactly is it testing for?

Essentially, what I'm asking is, what sort of measurments are these taken in. The TV-7 has a relative scale of 1-120, and for the Mutual Conductance button, I'm assuming it's measuring in MicroMhos.. but what about the Gas, Diode, etc. buttons?

Thanks!

 

[mkmelt]

Do you have a copy of the TV-7 user's manual? This may have the information you are looking for regarding 5727 tube and the gas test. You may have better luck posting your follow-up question on the Tubes Asylum board. There are some serious tubeheads over there.

http://www.audioasylum.com/audio/tubes/bbs.html

 

[vwap]

Quote:

Originally posted by mkmelt Do you have a copy of the TV-7 user's manual? This may have the information you are looking for regarding 5727 tube and the gas test. You may have better luck posting your follow-up question on the Tubes Asylum board. There are some serious tubeheads over there. http://www.audioasylum.com/audio/tubes/bbs.html

I should probably look for the original manual.. all I have is the test data manual..

Thanks for the suggestion

 

[vwap]

Okay.. so now that I understand what a triple mica is.. what exactly does a triple mica with extra support rods, and a triple mica without extra support rods look like? They all have rods holding them up, so how can you tell that one has 'extra' ones?

Thanks

 

[ServinginEcuador]

The only way to know what has extra rods or not is to first know how many it SHOULD have. If something, or a certain series of tubes, should have 4 rods, a tube with more than 4 has extra. Simple, huh?

 

[braillediver]

"extra support rods,"

Some tubes will have a set of rods (one rod on each side) running up between the bottom mica to the top mica, parallel to and in between the plates

[] l []

The third Mica and Extra Support Rods were added to make the internal tube structure more rigid so it would be less susceptible to vibration. With the goal of decreasing microphones and reducing mechanical failure caused by the vibration. Remember that tubes were used in aircraft in the 50’s and 60’s and were exposed to lots of vibration, which led to poor performance and premature failure. I believe the thicker Micas were also used to for the same purpose.


Mitch

 

[braillediver]

extra support rods

Mitch

 

[vwap]

Ah.. I get it now..

Thanks much Mitch, Doug, et. al. You guys are ever-so-helpful.


Man, you learn something new every day..