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Russian Teflon caps

Discussion in 'Tube Audio' started by nj pheonix, May 14, 2018.

  1. nj pheonix

    nj pheonix AK Subscriber Subscriber

    Messages:
    9,911
    Location:
    New Jersey
    The green ones are k42y-2s. I couldn't tell you what the difference between the silver and the green.
     

     

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  2. Selmerdave

    Selmerdave Well-Known Member

    Messages:
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    That's one of the first accounts I've read of K40-y9 failure.
     
  3. Brice

    Brice AK Subscriber Subscriber

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    1,495
    Location:
    Hoboken NJ
    Thanks Greg.

    Yes for me too. Never had one failed on me.
     
  4. GregBilodeau

    GregBilodeau AK Subscriber Subscriber

    Messages:
    66
    Location:
    Edmonton, AB Canada
    The one that failed on me was in one of my Dynaco MKIII's and only had maybe 10 hours on it. I was a little surprised for sure and at first did not even consider a capacitor failure. I had bought a whole box of them and since the failure I have not installed anymore just in case.

    Gregb
     
  5. Brice

    Brice AK Subscriber Subscriber

    Messages:
    1,495
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    Do you test them before installation? Maybe that one was leaking from the beginning and got worse over the break-in period.
     
  6. x3workshop

    x3workshop AK Subscriber Subscriber

    Messages:
    1,978
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    Harlem
    That’s quite unusual, but certainly not out of the question.

    I’m curious, did you test the caps at rated voltage prior to installation?
     

     

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  7. x3workshop

    x3workshop AK Subscriber Subscriber

    Messages:
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    I see Brice and I are thinking along the same lines... and at the same time!
     
  8. GregBilodeau

    GregBilodeau AK Subscriber Subscriber

    Messages:
    66
    Location:
    Edmonton, AB Canada
    I have a Sprague Teleohmic and test all old caps before installing. I have even started checking new caps for value just in case as I had one marked wrong that I installed in a TV horizontal circuit and I lost the last few hairs on my head trying to find that problem.

    Gregb
     
  9. Brice

    Brice AK Subscriber Subscriber

    Messages:
    1,495
    Location:
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    Interesting. Your tester is quite good.
    I wonder if my aging box would have trigger the failure. I would think so if I let it run for more than 10 hours I guess.
    Thanks for reporting your experience Greg.
     
  10. gadget73

    gadget73 junk junkie Subscriber

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    The older style cap testers do sort-of test ESR, but they call it power factor. Its testing for the same thing, but the old PF check was usually done at 120 hz and ESR checks are done at much higher frequencies. ESR is much harder to pass, but for caps that only ever see 120 hz its good enough. Its not too useful for audio frequency coupling or for stuff used in switch mode supplies.
     
    Bill Ferris likes this.
  11. Brice

    Brice AK Subscriber Subscriber

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    I didn't know that. Thanks Gadget.
     

     

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  12. Brice

    Brice AK Subscriber Subscriber

    Messages:
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    Hi Guys,

    I wanted to report on this topic.

    - I "cooked" 8 x 0.22uf 600V Teflon FT-3 for over 200 hours in two batches at around 520 VDC, with white noise going through the caps.
    - I checked the value and leakage after the cooking: nothing changed. Same value, 0 leakage.
    - I Installed them into 4 mono blocs, and respected the polarity of higher voltage in the amps.
    I am please to say that it worked ! :banana:

    The Teflon caps had their natural clarity from the beginning and haven't changed since.
    No dip dull sound after 40 hours and slowly back up, which is a nerve wrecking experience.
    I am listening to them as we speak. Superb sound.

    So to my experience, it is very worthwhile aging the caps before than burning your tubes and ears for 200 hours :p

    Cheers,
    Brice.
     
    drtool likes this.
  13. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
    2,750
    Location:
    Burlington, NJ
    Brice, why not share that setup that you built? I'm happy that it worked out for you. I'd be upset to hear something going down hill although from the experiences here it seems that you just have to grin and bear it for some hours and it comes back.

    BillWojo
     
  14. Brice

    Brice AK Subscriber Subscriber

    Messages:
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    Location:
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    Hi Bill,
    What I have done is a prototype really. Here is the detail.

    - I bought a Chinese PS from Ebay, 12VDC to 1KV for a few mA.
    - I bought a white noise generator kit from China also, 12VDC also.
    - I had a small plastic box so decided to reuse it. Made ventilation holes.
    - I remove the 100k linear mini pot from the HV supply and connected it to a "real" pot fixed in the box.
    - I added a 0.1uF 600VCD caps, from the output of the white noise generator
    - Added a switch to power the white generator board or not.
    - Added a 3.9M resistor and a LED to the HV supply out, to indicate the presence of HV and to load the supply. This is very handy to have.

    Here is the schematic and the pics of the boards.
    I hope it helps
    Brice.
    20180712_130454.jpg schematic.JPG
     
    Dandy likes this.
  15. primosounds

    primosounds SE KT120 w/ 6J5G drivers. Subscriber

    Messages:
    2,717
    Location:
    Terra, 21st century CE
    the Dynaco MK3 has very high voltages especially if the 5ar4 rectifier has been replaced by a SSR. The initial voltage surge from that set up can be over 600v. If you couplling caps were only rated to 600vdc that may have been exceeded. Any cap with a 600v rating would have a hard time in that situation. I would not blame the cap without more info about the amp and its design.
     
    Brice likes this.
  16. GregBilodeau

    GregBilodeau AK Subscriber Subscriber

    Messages:
    66
    Location:
    Edmonton, AB Canada
    Mullard GZ34 rectifier, no SSR ever in this amp. The caps were a matched set supplied with the amp. The amp is the Latino ST120, what more would you like to know.

    Greg
     

     

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  17. ConradH

    ConradH Addicted Member

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    It happens now and then with just about everything. I wouldn't panic unless you see a few fail. Film caps will usually support far more voltage than the rating. I don't know if they test them to 2X or more, but I doubt the Dyna would bother any that were up to snuff to begin with. The HV test before use is always a good idea if you want to be really confident. Losses can be specified as dissipation factor, power factor, ESR and a couple other ways. IMO, the losses of a Teflon cap are too low to measure with any common equipment. If you think you see something greater than zero in terms of DF, PF or ESR, it's almost certainly measurement error. I did a page on losses a while back- http://www.conradhoffman.com/cap_losses.htm
     
    Retrovert and primosounds like this.
  18. primosounds

    primosounds SE KT120 w/ 6J5G drivers. Subscriber

    Messages:
    2,717
    Location:
    Terra, 21st century CE
    I agree. It seems that if the Latino ST120, has not been used for over 2 or 3000 hours, ripping out all the coupling caps when just 1 went bad is somewhat of over kill. Unless, you were looking for an excuse to try a different type of cap, in which case that would be a good time to do that.
     
  19. arts

    arts Super Member

    Messages:
    3,716
    Location:
    Qc, Canada
    Brice,what kind of white noise amplitude are you able to superimpose on the DC level?
     
  20. Brice

    Brice AK Subscriber Subscriber

    Messages:
    1,495
    Location:
    Hoboken NJ
    Only 1 V at max amplitude, there is a miniature pot on the white noise generator.
     

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