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Need Confirmation to the quality of this Valve / Tube?

Discussion in 'classic' started by beammeup, Oct 9, 2019.

  1. beammeup

    beammeup pfm Member

    After rummaging through a box of valves / tubes - this looked interesting?

    Just checking with you Fishies if this is good 'bottle' or not. I'm not 100% sure.

  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Good in what way? It's a very old example of a 5U4G rectifier... If gettering looks OK it probably works. Can't see it properly in that photo... maybe some around the bottom...
    Is that an EF50 I spy to the left, red with metal base?
  3. beammeup

    beammeup pfm Member

    I just wondered if it was worth something decent.

    Yes there are at least 4 Mullard EF50's in that box.
  4. ducatiman

    ducatiman pfm Member

    £150 IF tests well, probably a third of that untested
  5. beammeup

    beammeup pfm Member

    Not bad then! Over a ton for just 1x valve means it's of some decent value - thanks for your assessment.
  6. Tony L

    Tony L Administrator

    Looks like a nice vintage American 5U4, as Jez says as long as it is still sealed, i.e. has silvering around the getter(s) on the glass it may well be fine.

    PS I welcome any donations of unwanted EF50s as the vintage valve computer (Manchester SSEM) I demonstrate to people at the museum uses tons of them and we could do with more stock!
  7. Vinny

    Vinny pfm Member

    The getter is the "silver" mirror" on the glass. It evaporates from what are normally rings (although the source can actually be any of many shapes/sizes) when the are heated by induction, after the valve is evacuated and sealed (tipped-off). Unfortunately, even within the industries using them, the rings or whatever are fired to generate the actual getter film/mirror, are routinely called getters, indeed, even Saes (who were or are, BY FAR the largest supplier in the world) called the rings getters.

    In most cases, and certainly in the case of "mirrors" it will be barium, which reacts with water and particularly oxygen. It is there primarily to clean-up the gas that remains in the glass bulb after it is exhausted and sealed. (Contrary to popular belief, there is still LOTS of gas inside a commercially evacuated bulb of any kind, valve, lamp or anything else.)
    If there is a leak, you get barium oxide formed, which is white and powdery.
  8. Tony L

    Tony L Administrator

    These days the term ‘getter’ certainly refers both to the silvering and the wire assembly that deposits it in initial flashing in production, e.g. you’ll see valves identified by having ‘ring’, ‘square’, ‘goal-post’ etc getters.


    Here’s an otherwise lovely mid-50s vintage fat-base dual ring-getter Mullard GZ34 that has sadly lost its vacuum. It would easily be a £100+ valve if it still worked!
  9. Vinny

    Vinny pfm Member

    The use of the word getter by Joe Public is akin to the "etched" ID on valves, the use of the word bulb and much besides. Incorrect.

    The getter is the barium film, not the rings. The rings are just soft iron, U cross-section, rings.
  10. Tony L

    Tony L Administrator

  11. beammeup

    beammeup pfm Member

    The box is in an auction due tomorrow - if I win - you can have all the EF50s in there for nothing.

    Here's one I picked up during my rummage:


    Next to this weird looking tube here:

    Tony L likes this.
  12. ducatiman

    ducatiman pfm Member

    I could sort you some are you at the upcoming hifi show
  13. Tony L

    Tony L Administrator

    Thanks, not that I’m aware of, which show? Happy to pay postage!
  14. Darmok

    Darmok "A Priori Teleology."

  15. snowman_al

    snowman_al pfm Member

  16. beammeup

    beammeup pfm Member

    Sorry Tony - I didn't win the auction - so no box of valves for me. I put £35 on the box and they went for £40 ...

    Ah well ....
  17. Tony L

    Tony L Administrator

    No worries. Always hard to know what to bid on that sort of thing, especially for unboxed stuff.

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