Power Tube Question

Nightfall
Nightfall Posts: 10,042
Is it normal for a 5U4G power tube to glow purple, flicker purple, etc. when it's first turned on? I don't recall ever seeing this happen. Even after they settle down there's still two small sections of "wire" (filament?) inside the tube that stay purple until the tube has been powered up for several minutes which the purple then goes away completely. I feel like this is an indication that the tube is on it's way out or is somehow leaking but thought I'd ask the forum since after it totally warms up it looks like normal. Should I pull and trash it?

Sorry for the horrible picture. I don't have a tripod and close up shots the shutter stays open so long that I inevitably move the camera.

besiowu.jpg
afterburnt wrote: »
They didn't speak a word of English, they were from South Carolina.

Village Idiot of Club Polk

Comments

  • Nightfall
    Nightfall Posts: 10,042
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • mhardy6647
    mhardy6647 Posts: 32,926
    edited August 2018
    Not normal in a 5U4 IME & to the best of my knowledge. My guess is that it's "gassy" = bad. Now, it is possible that it's a symptom of another problem (specifically, excessive current draw by the components "downstream" of the HV rectifier), but it may well also be (as an MD would put it) idiopathic. I.e., it's gone bad because... it's gone bad B)

    Is that, by any chance a "modern" 5U4 (more to the point, a Chinese or even Russian tube)?

    I'd replace it, were it mine. Do you have access to a tube tester?

    https://hackaday.com/2015/01/17/vacuum-tube-repair-after-a-spectacular-failure/
    http://k5jxh.com/odds-ends/gas.html
  • marvda1
    marvda1 Posts: 4,862
    Nightfall wrote: »
    Is it normal for a 5U4G power tube to glow purple, flicker purple, etc. when it's first turned on? I don't recall ever seeing this happen. Even after they settle down there's still two small sections of "wire" (filament?) inside the tube that stay purple until the tube has been powered up for several minutes which the purple then goes away completely. I feel like this is an indication that the tube is on it's way out or is somehow leaking but thought I'd ask the forum since after it totally warms up it looks like normal. Should I pull and trash it?

    Sorry for the horrible picture. I don't have a tripod and close up shots the shutter stays open so long that I inevitably move the camera.

    besiowu.jpg

    this is a rectifier tube not a power tube.
    Amplifiers: Norma IPA 140, MasterSound Compact 845, Ayre v6xe, Consonance Cyber 800
    Preamp: deHavilland Ultraverve 3
    Dac: Sonnet Morpheus 2, Musical Paradise mp-d2 mkIII
    Transport: Jay's Audio CDT2 mk2, Lumin U1 mini
    Speakers: Rosso Fiorentino Volterra II
    Speaker Cables: Organic Audio Organic Reference 2
    Interconnects: Argento Organic Reference 2, Argento Organic 2
    Power Cables: Argento Organic Reference, Synergistic Research Foundation 10 and 12 ga.
    Puritan PSM156
  • Nightfall
    Nightfall Posts: 10,042
    edited August 2018
    It's an old RCA.

    Thanks for the correction Marv.

    I'm pretty sure the only other 5U4G I have is the Chinese one that came with the preamp. I'll see if I can find it.
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • codycatalist
    codycatalist Posts: 2,662
    I mean I don't know much about tubes but did do some research on Google. I found a thread where a gentleman described his tube looked like a Tesla coil for a second then stopped.

    To me it looks like a Tesla coil but you are the better judge of that...he replaced the tube and all was well after that. Granted this was a different tube type (EL84) but here you go if you want to read and see if it matches up to what you see.
    Just a dude doing dude-ly things

    "Temptation is the manifestation of desire which equals necessity." - Mikey081057
    " I have always had a champange taste with a beer budget" - Rick88
    "Just because the thread is getting views don't mean much .. I like a good train wreck doesn't mean i want to be in one..." - pitdogg2
    "Those that don't know, don't know that they don't know." - heiney9
    "Audiophiles are the male equivalent of cat ladies." - Audiokarma Member
  • mhardy6647
    mhardy6647 Posts: 32,926
    True although, of course, a 5U4/5U4G/5U4GB HV rectifier is a high power tube in most audio applications (all the HV juice, at least, flows through it!) and dissipates a lot of heat, akin to a power output tube.

    hnqbw4m17gxf.png
  • Nightfall
    Nightfall Posts: 10,042
    I just meant power as in involved with power delivery to the preamp, not as in amplification power. The 6V6 in there is also in that same category. It made sense in my head, if incorrect.
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • mhardy6647
    mhardy6647 Posts: 32,926
    edited August 2018
    As the RCA manual scan I posted indicates, an HV rectifier like that one is indeed considered a "power-handling tube", so you're good. Folks with hifi interests probably tend to think of power output tubes when they see "power tube", which is OK, too.

    Now, if you start calling, say, EL34s tetrodes, well, then... we'll have to have a little discussion, methinks.

    ;)

    PS the RCA scan is from RCA Receiving Tube Manual RC-23 (from 1964).
    If you don't have any (all!) of the tube literature at Pete Millett's wonderful site... you should. :)

    http://www.tubebooks.org/tube_data.htm

    Lots of other wonderful things on Pete's site, plus, like Nelson Pass, he has a comprehensive and excellent site of DIY projects, too @ www.pmillett.com :)



    ebnm1515d0et.png


  • mhardy6647
    mhardy6647 Posts: 32,926
    edited August 2018
    oops, derp... misfire.

    sowwy.