Scarce rectifier tubes...

Discussion in 'Tube Audio' started by soundmotor, Apr 14, 2018.

  1. soundmotor

    soundmotor super modified Subscriber

    My re-org of garage / storage / decades old mess continues on the way to a clean & functional shop. I found these stuffed away in one of the recesses. They are a Genalex U52 (5U4G) & U77 (5AR4), Mullard GZ33 (super 5AR4), and an RCA 5690 red base (derated & indirectly heated 5Y3). The 5690 a real odd duck and looks like a fatboy 5692. I do miss the old Sunday morning school cafeteria hamfests...

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  2. primosounds

    primosounds Parallel single ended EL84 ,EDCOR OPT Subscriber

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    The 5690 is a 12.6v rectifier. I guess it was made ultra rugged for missles or aeronautics. I got a handfull of them but not really useful in commercial audio and probably only seen in military. If you were designing your own amps they would look impressive, which is why i bought them. But specs wise they are not as good as 5ar4
     
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  3. soundmotor

    soundmotor super modified Subscriber

    I'd forgotten that about the filament voltage, what a weird tube. I got it pre-internet and it was a long time before I found out much on it. You are the only other person I've come across that had any. For a long time I looked for another but never found one and stopped. As far as ratings, I'd bet derating applies to the current spec on it like many military electronics items. It may ahandle more and the parameters are not the actual but well less of it. Agree it is a cool tube, maybe in a preamp someday with some 5692s.
     
  4. soundmotor

    soundmotor super modified Subscriber

    I'll say this for doing a deep dive on layers deep stuff, it's somewhat kickstarted my interest in building again. Been a looong time since I've done something from scratch.
     
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  5. kvflyer

    kvflyer AK Subscriber Subscriber

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    I think that you will find that the 5690 is two separate rectifiers in one envelope. Both heaters could be connected in parallel for 6.3 volts.
     
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  6. soundmotor

    soundmotor super modified Subscriber

    I believe you are correct -

    https://www.radiomuseum.org/tubes/tube_5690.html



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  7. Joe Roberts

    Joe Roberts Agent Provocateur Subscriber

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    I have have had 3 or 4 of those RCA 5690s for decades. Lots of cool things can be done with them thanks to separate cathodes. Full wave bridge, tube voltage doubler, etc.

    Did I ever do any of this....no! I just hoarded the tubes.

    I seem to recall that the WE 412A is set up like this as well.
     
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  8. soundmotor

    soundmotor super modified Subscriber

    I spent yesterday grouping all the tubes in one spot and last night at Target putting the unified tote theory into practice. I can't believe the quantity amassed from back when.

    Easy to do when they were ~$1 each.
     
  9. primosounds

    primosounds Parallel single ended EL84 ,EDCOR OPT Subscriber

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    Very good point KV. It is knowing how to manipulate what you have to work with that will allow you to get the most out what you are using.
     

     

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  10. Dswankey

    Dswankey Super Member

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    What other tube did you uncover?
     
  11. Mike Stehr

    Mike Stehr Poverty Audio

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  12. soundmotor

    soundmotor super modified Subscriber

    It's not a huge stash of stuff but I was surprised by some I'd forgotten about. Here's a few, WE 211A & a 102F -

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    I don't know what the A1757 is. The 439A is a trochotron, 10-line in switch tube for a decade counter or early computer -

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  13. soundmotor

    soundmotor super modified Subscriber

    These in much coveted DIB condition, Dud In Box, Amperex 5AR4s w/ F32 code, darn -

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  14. Dswankey

    Dswankey Super Member

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    ^ That Sucks!!
     
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  15. soundmotor

    soundmotor super modified Subscriber

    Yup. Palate cleanser after that disappointment, NU 5Y3G, pre-war w/ ribbed plates. Cryptic chicken scratch runes (mine) from decades back give hope these are OK.

    If so, project bound! I've never seen another set before or after these.

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  16. Dswankey

    Dswankey Super Member

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    Wow!!, those are interesting looking
     
  17. soundmotor

    soundmotor super modified Subscriber

    The next ones I post even more so.....

    :banana:
     
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  18. Dswankey

    Dswankey Super Member

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  19. primosounds

    primosounds Parallel single ended EL84 ,EDCOR OPT Subscriber

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    Euro 5y3 GZ30/32 from WW2 era are also very interesting/different construction.
     
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  20. Retrovert

    Retrovert AK Subscriber Subscriber

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    I don't think that works because the heater resistance is designed to heat based upon the operating voltage. With the two heaters (resistors) in parallel, the cathode temperature will be far below what it should be because each heater is operating at a lower voltage. While the circuit impedance is now correct, the heater temperature is not.

    This is a different situation than wiring two heaters (resistors) in series since each drops 6.3 V for a total of 12.6 V. In such circumstance each heater would be at the correct temperature.

    String heaters do have issues, of course, because the string forces current through a heater which is already at operating temperature. If the string is small this issue is smaller. This is why string heaters are designed to have identical warmup times, although individual variations can force current through a high-impedance heater, damaging it. Remember, the tungsten has a PTC so its resistance increases as the heater temperature increases. That's why the heater does not have thermal runaway.

    So parallel heaters to match the lower operating voltage will likely not work as the heaters will both be too cool for proper rectification.
     

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