PREVENT UNDUE HEAT

Discussion in 'The Workbench' started by VERVEHAMMER, Sep 20, 2021.

  1. jmp45

    jmp45 Well-Known Member

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    Thanks Verve.. I opted for something that didn't need any attention. I don't care for the fan noise, but then not that I could hear it with the Major cranked up.. ;)

    I guess if you know what temperature you'd like to maintain in the head cab you could install a thermal switch value to keep it there. Mounted on top, inside but not directly above the output tubes.
     
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  2. VERVEHAMMER

    VERVEHAMMER Active Member

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    ...but then not that I could hear it with the Major cranked up.." ;)

    HA! : )

    No Kidding. So Loud you have to stand to the side or it'll make you sterile.

    :headbanger:
     
    Last edited: Sep 22, 2021
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  3. jmp45

    jmp45 Well-Known Member

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    I haven't heard crickets in years ;)

    [​IMG]
     
  4. VERVEHAMMER

    VERVEHAMMER Active Member

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    Outstanding Loud Quality....
    I try to explain Marshall to others, like Marshall does. marshall ad.jpg

    "just because it's loud, doesn't mean you'll want to listen to it"
     
    Last edited: Sep 22, 2021
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  5. PelliX

    PelliX Well-Known Member

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    What's in the racks to the left of the AC30?
     
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  6. jmp45

    jmp45 Well-Known Member

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    A bunch of old gear. I use the g-major > graph > 9005 power amp > 2 1x12 v30 cabs for w/d/w out to the back side of the space 99% of the time out from the SLP. I patched so I can run the racks with the other preamps and processors how I link in the homey patch bay bottom of the 12 space.

    [​IMG]

    [​IMG]
     
    Last edited: Sep 22, 2021
  7. Pete Farrington

    Pete Farrington Well-Known Member

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    I think that valve manufacturers expect the ambient conditions that the valve is in to be reasonable, with equipment cabinet designed such that there's air circulation around the valve bulb.
    The KT88 info notes a max bulb temperature of 250C, see p2 'Installation' of https://tubedata.altanatubes.com.br/sheets/084/k/KT88.pdf

    As with standby, I've always considered that to be a hypotheses that somehow became ingrained in the folklore of the valve guitar amp.
    Is it documented anywhere (ie that has some degree of technical credibility)?
    I think that once power is removed, valves cool down pretty quickly; the minute or 2 it'll take to shift guitars / cables / pedals off stage first at changeover should be plenty.
     
  8. VERVEHAMMER

    VERVEHAMMER Active Member

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    Thanks Pete, I always appreciate your contributions.

    I've seen premature tube failures from rough handling while still hot, firsthand myself.

    No citation needed for me. Personal experience. Since I have to fix any problems, I decide for myself. as all Users should.

    "reasonable"

    "pretty quickly'

    "should be plenty"

    Your Mileage May Vary.... : )
     
    Last edited: Sep 22, 2021
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  9. PelliX

    PelliX Well-Known Member

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    That's a nice rig and an impressive room you've got there, I like 'em! I'd have given 10 of 10 points, but I don't see the Tele... :D
     
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  10. jmp45

    jmp45 Well-Known Member

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    Yep a tele would be cool. I'm been considering a 73 8x10 cab for the small box.... but I've run out of space ;)
     
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  11. MP+

    MP+ Member

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    Just speaking from getting around a major overheating issue, I found that all the heat build up ended up being routed to the power transformer. My amp still runs hot, but just nice hot, not overheated hot, right where it should be. As described in my earlier post, a fairly small super quiet DC fan right in close to the power transformer just pulling air over it did the trick big time rather than a massive noisy fan blowing air everywhere. I just secured the fan direct to the timber adjacent to the power transformer having the heatsink in hard contact with the timber. The drawn air dissipates through the heatsink fins and further deadens any fan noise or ringing of the fins. Seriously, if you didn't know there was a fan in there, you would not pick it, the noise is right down with the level of switch on hiss with all levels set to zero.
     
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  12. alpha al

    alpha al Active Member

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    No, it blows onto the chassis. That chassis was getting so hot, you couldn't hold your hand on it. I was afraid for the capacitors. Now it doesn't do that.
     
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  13. MP+

    MP+ Member

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    Just getting this in context with my story, the chassis itself can't heat up, it's overheating components dissipating onto the chassis. My situation was in an under ventilated head, so it was easy to pinpoint and target the single major component that ended up out of control more than any others, and that was the power transformer. I'm guessing that you are dealing with an amp. which has the components inverted, or facing downwards so that heat is rising into the chassis which turns into one large heat sink. In my case, you could barely touch the outer case around the power transformer. Once I set up small, quiet, targeted cooling fan, the amp. is electrically immaculate. If I was doing the same with an inverted combo, I would find a good mounting point for the heat sink fan, which actually does end up working like a remote heat sink, and run some sort of duct right up close to the power transformer.
     
  14. XTRXTR

    XTRXTR Well-Known Member

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    What is the Volt and Amp rating of the fan. You could build a permanent mains ac connection that would then run to a voltage divider and a rectifier that is appropriate for the fan. Run the wires through the same hole of the PT primary to the top of the chassis and use a 5, 9, or 12V plug that hangs where you need it. I like having everything set, all connections in place within reason, open the case plug n play.
     
  15. alpha al

    alpha al Active Member

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    I've replaced several power transformers in those amps because of an open primary. They have an internal thermal fuse that is not replaceable. But the heat is not coming from the transformer, it's the power tubes heating the chassis.
     
  16. Pete Farrington

    Pete Farrington Well-Known Member

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  17. MP+

    MP+ Member

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    Without doubt, once that power transformer takes off, you might as well get the bacon and eggs ready. The only additional thought that crossed my mind with the "upside down" combo was possibly setting up a tube (as in hose, not tube as in valve) in that cavity above the chassis and below the cabinet roof, then connecting this to a small fan that would work as a heat extraction fan. Grab the heat after it has risen but before it runs wild.
     
    Last edited: Sep 24, 2021
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  18. MP+

    MP+ Member

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    I think mine (power transformer) was on the verge of blowing. Once the heat takes off the whole issue turns into a spiral. The power transformer ends up overheating due to its physical mass and copper content, the valves get hot, but they alone couldn't produce enough heat to make a chassis red hot. For me, cooling the power transformer did the trick, but every different amp. will require its own specific approach.
     
  19. junk notes

    junk notes Well-Known Member

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    Yes, and that was the point *they were making, describing that the apparatus around the glass of a vacuum tube is incubating; shortening or not necessarily extending tube life.
    (*audiophiles IIRC)
     
  20. junk notes

    junk notes Well-Known Member

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    ha! classic "my amp sounded its best when.." :fever:
     
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