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Information - Help 
ID = 25617
Brand: Tesla; Praha, Bratislava etc.
Tube type:  Vacuum Pentode   RF/IF-Stage   Controlling (mu) 
Identical to EF9nT
Similar Tubes
Heater different:
  AF3 ; EF3
Multiple differences or of other kind:

Filament Vf 6.3 Volts / If 0.41 Ampere / Indirect / Specified voltage AC/DC
Description This is an AF3, fitted with a 6.3 volts heater, as a makeshift replacement for the EF9. Actually this is an EF3, though with 0.41 A heater current. 
Text in other languages (may differ)

ef9nt_so.png EF9nT: rtt
Anonymous 10 Collector

EF9nT: Tesla catalogue
Gabriel Toth

Collection of



Forum contributions about this tube
Threads: 1 | Posts: 7
Hits: 2508     Replies: 6
Tesla EF9n T
Jose Vigil
  1 Dear Gentlemen.
I have a Tesla valve in his original box.
On the box there is the mark EF9.
But the valve itself is marked EF9n T.
It is rather different to current EF9's, larger in all dimensions. Aluminum color, not red.
I wonder if anyone has references for this tube.
Best regards, Jose
Robert Sarbell † 22.3.22
  2 Hello Jose,

It is quite possible that a manufacturer in one of the German-speaking countries in the very late 30s or early 1940s may have placed the letter "N"suffix (or "n") on the tube body to indicate it was a "nachfolger" version of the original EF9. The word nachfolger means "successor" . . . . . .and frequently the tube base could be changed. If the maximum plate voltage capability was increased, then the value would be added to the suffix.

Typically the suffix letter N indicated a followon variant of an original tube. A number of tubes used the newer P8A base instead of the earlier Au8 (aussenbelag) base - which had the outward facing pins. Additionally the tube would have a different envelope shape and often a lower overall heighth.

You could submit photos of the box and the tube to the tube administrators, and if approved, then your photo will added to the EF9 tube database.

Gabriel Toth
  3 Dear Jose,
company Tesla was founded in second half of 1946. However, directly after WW2 it was not acceptable to use in CS any German shortcuts.
I found in Tesla catalogue the electrical parameters of EF9N, the specified dimensions are 43x106mm.
After WW2 was a very big lack of tubes in Europe and in CS too. Moreover, the government nationalized the Philips company too and the import of tubes was not possible more. The government had to built very urgently a new CS company for tubes production. In city Roznov pod Radhostem they had been grown up a tube manufacturer company. In the beginning here did not exist any deep research and development - only a copying of existing foreign tubes. It could happened, that the electronic industry needed some kind of tubes, but the development was not finished or on stock trhey had older tubes bases only. From this reason we could find some intermediate kind of tubes - with label N, in Czech means new or successor. I have seen for example EBL21 tubes instead of octal in side pin version!
I think, it could be better to have in database tube EF9N too (see AL4 and AL4n), the heating current is different.
Jose Vigil

Dear Gabriel.
Thanks for the information of the Tesla Company.

Filament current with a nominal 6.3V applied on the socket terminals is 448 mA.

There is also one letter "T" added alongside the EF9n marking.
Perhaps it has some meaning too.

Best regards, Jose

Jose Vigil
  5 Hi Robert.
Thanks for the information.
Today I uploaded three photos.
One of the valve and the box. With a ruler in inches and mm on the side of the valve.
The second shows the marking on the box.
The third shows the Tesla and a Philips EF9. For comparison purposes.

Best regards. Jose
Ernst Erb
  6 Please never put pitures to a tube named differently.
Ask for a new tube if you have the proof and hopefully some information.
I did notw enter a new tube EF9nT - but it is "late" and I did not care about data - but I moved the pictures.
Robert Sarbell † 22.3.22
  7 Gentlemen,

Please accept my apologies for my suggestion to Mr Jose Vigil above re: the statement that upon approval the administrators would enter the data into the EF9 database. . . .

Regarding my comments, my most accurate wording should have stated that upon review by the tubes administrators [please note there is an official "Rohrenadmin" staff], THEY will determine the most appropriate entry for the tube(s) being submitted.

There is still some doubt by relatively new members as to the exact procedure to follow when submitting new tube images. The following sentences are extracted verbatim from the "newesttubeimages" page in RMorg.

Every member can load up tube photos. Suggestions for new tubes have to be handed over to a tube administrator listed on the main tube page. You reach this by clicking the tab "Tubes" where you also find the "Search for a tube".

End of forum contributions about this tube

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