12SN7

Thread Starter

AlbertHall

Joined Jun 4, 2014
11,129
I wa watching a film when the radar operator had a problem with his equipment. He called out "Bring me a 12SN7!". This immediately awoke memories of long ago and I could recollect that a 12SN7 is a double triode with a 12V heater. I was surprised at this detail as there can't be many around that would recognise this valve (or vacuum tube if you prefer).
 

Ian0

Joined Aug 7, 2020
1,618
I'm always amused by the "GT" variant, as if it might be some fantastic souped-up version; only to find out that it stands for "Glass Tube"
 

Reloadron

Joined Jan 15, 2015
5,888
After all the years it seems certain vacuum tube or valves part numbers seem to stick with us. The 5Y3 and 5U4 rectifiers and before them the Type 80. Low power guitar amps the 12AX7 as a pre amp and the 6L6. Had a ham friend who figured you could do anything with a 6L6. :) Life was good during the 50s and early 60s for war surplus stuff. My first ham transmitters were ARC5 command sets and I think I still have a pair of 1625 tubes, the finals. My first Heathkit DX 40 using a 6146 final. Anyway certain tube / valve part numbers seem forever imprinted in our minds. :)

Ron
 

Reloadron

Joined Jan 15, 2015
5,888
I've taken apart enough cheap tube-type radios to remember the lineup was some variant of 12AV6, 12BE6, 12BA6, 50C5, and 35W4.
Exactly what I was getting at. Certain tube part numbers are like burned in out mind. Tubes like the 50C5 beam pentode and 35W4 half wave rect were real popular when they started putting filaments in series eliminating need of a 6.3 or 12.6 volt filament source.

Ron
 

MisterBill2

Joined Jan 23, 2018
8,230
The 6SN7 and 6SL7 were unique octal tubes in that the heater connections were pins #7 and #8, while almost all other octal receiving tubes have the heater connections on pins 2 and 7. And I actually did have the indicator section of an old radar set that did use a whole lot of 6SN7 tubes. But no 12 volt tubes. So the scene was sort of accurate, except that it is hard to imagine that a radar operator would know to replace a tube if something failed.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
11,129
The 6SN7 and 6SL7 were unique octal tubes in that the heater connections were pins #7 and #8, while almost all other octal receiving tubes have the heater connections on pins 2 and 7. And I actually did have the indicator section of an old radar set that did use a whole lot of 6SN7 tubes. But no 12 volt tubes. So the scene was sort of accurate, except that it is hard to imagine that a radar operator would know to replace a tube if something failed.
And he knew which tube to replace without even taking the cover off. This was in a US submarine in 'Up Periscope'.
 

nsaspook

Joined Aug 27, 2009
8,168
The 6SN7 and 6SL7 were unique octal tubes in that the heater connections were pins #7 and #8, while almost all other octal receiving tubes have the heater connections on pins 2 and 7. And I actually did have the indicator section of an old radar set that did use a whole lot of 6SN7 tubes. But no 12 volt tubes. So the scene was sort of accurate, except that it is hard to imagine that a radar operator would know to replace a tube if something failed.
Many operator positions on a sub are dual function. The operator is also the technician.
 

Reloadron

Joined Jan 15, 2015
5,888
And he knew which tube to replace without even taking the cover off. This was in a US submarine in 'Up Periscope'.
Going back a few short years, maybe around 1970 I did some training at a Naval NARF (Naval Air Rework Facility) for the then in use ARN 21 TACAN Simulator. Large and heavy stack of equipment with endless tubes or valves. The gentleman I had the privilege of working with and learning from knew that thing inside out and then some. Fire that thing up, look at a few signals on a Tektronix 545B with 1A1 plug in and he could tell you which tube failed or was failing. The amazing part was this was not a movie but real life. Over 50 years later I remember that like it was a week ago. The guy was good, I mean really good.

Ron
 
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