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Posted by CV4109 (D) on June 30, 2009 at 21:52:04

In Reply to: RE: Mystery 12AU7 = RFT posted by Thermionic27609 on June 30, 2009 at 20:33:08

A Google image search revealed them to be RFT production, one marked 7-51, the other 9-51. (1967? 1969?)

- RFT/East German Small Signal tubes have a peculiar glass bottle that is easy to recognize if you see enough examples.

- If your tube looks like RFT, then it is. Production could be anywhere from 1960s-1980s. 7-51, the other 9-51 numbers do not relate to the actual production years. If you can post pictures, it will be easier to confirm the decade.

These are not Mullards or Amperex for sure. Decent tubes otherwise.

• RE: Mystery 12AU7 = RFT - Thermionic27609 14:05:58 07/01/09 (3)
  In Reply to: RE: Mystery 12AU7 = RFT posted by CV4109 on June 30, 2009 at 21:52:04

  

  Yes, there's no mistaking the RFT tubes for anything else. The construction is very distinctive: folded plates more like some 12AT7s with three holes and a very heavy-duty getter support. Tube envelopes are large in diameter with unusually flat tops.
  
  I find it difficult to get a good tube photo with my digital camera, but here's a link with one with the exact construction. The labeling is the only difference.
  
  With the date codes, I would think they would be 1960s or maybe 1970s. Was RFT still making these in the 1970s? That might explain why they're Amperex labeled with their East German origin disguised. Or would Hewlett Packard have been making anything with tubes in the late 1970s?
  

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  • Late 1970s production - CV4109 16:26:33 07/01/09 (2)
    In Reply to: RE: Mystery 12AU7 = RFT posted by Thermionic27609 on July 01, 2009 at 14:05:58

    HP did not make tubes.
    
    These would be late 1970s-early 1980s RFT E. German production. Similar to these in the link below:
    
    

    • RFT ECC82 Single Support Halo - East Germany   (Open in New Window)

    
    

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    • RE: Late 1970s production - Thermionic27609 22:17:18 07/02/09 (1)
      In Reply to: RE: Late 1970s production posted by CV4109 on July 01, 2009 at 16:26:33

      CV4109,
      
      What I meant was: was HP producing anything that used vacuum tubes in the late 1970s? Or were they simply supplying HP branded tubes as replacement parts?
      
      David
      

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      • RE: Late 1970s production - CV4109 16:59:03 07/03/09 (0)
        In Reply to: RE: Late 1970s production posted by Thermionic27609 on July 02, 2009 at 22:17:18

        Perhaps some RF/Microwave/Instrumentation gear using tubes was still being made in late 1970s by HP but not totally sure. Since tube based instruments like scopes, signal generators etc. were in use through 1980s in labs across the country, there was a lot of service components in the distribution channel.
        
        Tubes were still being made until mid-1980s by companies like Tungsram, RFT, BEL India etc.
        

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