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  • GuitarTubeAmpPowerTrannyHeatRemoval

    There are no posted threads for using finned heatsinks embracing the tranny as passive radiators to the ambient air surround - why is this heat removal method (passive means no vibrations imparted).
    what is the method to calculate fin radiators geometry size dendritic reach and materials for optimal waste heat removal? bigger is not necessarily better, right? heat jumps outwards of the tranny by conduction and into the thermal conducting sticky adhesive and then into the finned substrate, then it moves toward the coolest temperatures in the finned substrate which are the fingers, tapered, then natural convect from the dendritic finger tips out into ambient air.
    i noted steady state dc high tension with a propeller fan and without, it is not negligible, 317 versus 296 dc volts for the quartet el84 in cathode bias class A pushpull. of course the sound gets richer as voltage drops, witout forced convection cooling of the tranny. but tranny longevity is being shortened by higher temperatures which slowly compromises the windings insulatory properties. tranny replacement is expensive, so isn't it prudent to operate at lower temperatures?
    there are so many varieties of finned substrates available to select from, and, nobody knows whether introducing all this additional metalized surface area has consequences of aerial antennae audio signal impact, that's why we shield can the ecc83 preamp tubes for shielding impinging radiation.
    thanks in advance.

  • #2
    I'm not an engineer but it seems like one would have to know the square inches of available surface, the dissipation rate based on that surface area and the thickness of the aluminum or copper, and how far you want to drop the temperature.

    I think it would be easier given the space involved in most boxes to install a fan and filter the power. Maybe using an AC fan to keep the DC issue at bay. Also you have to remember that sticky adhesive will act as an insulator, not a dissipation method which will keep heat in the transformer and possibly develop hot spots. That's not good either.
    --Jim


    He's like a new set of strings... he just needs to be stretched a bit.

    Comment


    • #3
      Although the EL84's get very hot,the PT shouldnt.If its getting too hot there is something causing too much current,better to fix the problem then to try to dissipate heat that isnt normal.

      Comment


      • #4
        I agree with stokes. Power transformers shouldn't get too hot. Only hot. The heat shouldn't be a problem unless it's cramped together with all the other heat producing components of the amp. In which case the power transformer heat isn't he problem, the layout is. So...

        In the event of a hot layout a fan and venting have always been the typical cure. Finned heat sinks for the PT still wouldn't make much sense because:

        1)The PT is pretty much a block of iron. Short of a very custom and large heat sink it would be tough to do much good.

        2) The PT shouldn't be the primary source of overheating problems. Rectifier and power tubes followed by resistors dissipating high current are most likely to cause excessive heat.

        So, with the above consideration I would say the best solution to too much heat is proper layout. Sans that you can do some venting and if that still won't do it you'll need a fan.

        Some failures or improper adjustments can cause a PT or tubes to operate abnormally hot. In these cases the amp needs fixing. If you have an amp that's not known to suffer heat related problems it may need repair.
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "If you're not interested in opinions and the experience of others, why even start a thread?
        You can't just expect consent." Helmholtz

        Comment


        • #5
          Wow.

          Sounds like a good argument for using Darkness Emitting Diodes (DEDs).
          Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

          Oh, wait! That sounds familiar, somehow.

          Comment


          • #6
            Originally posted by R.G. View Post
            Wow.

            Sounds like a good argument for using Darkness Emitting Diodes (DEDs).
            I've converted LED's to DED's by forgetting the current limiting resistor...

            Comment


            • #7
              Me too! It was a true epiphany when I realized that some bulbs are so dim they suck the light out of their surroundings.
              Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

              Oh, wait! That sounds familiar, somehow.

              Comment


              • #8
                Put more plainly...

                Some things shed light. Others just suck.
                "Take two placebos, works twice as well." Enzo

                "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                "If you're not interested in opinions and the experience of others, why even start a thread?
                You can't just expect consent." Helmholtz

                Comment


                • #9
                  If you must get rid of heat then there are on-line calculators to save you wading thru' the theory.
                  You will still need to understand the basic "Ohms Law" of ThermoGodDamnics (ThermoDynamics) and Thermal Resistance.
                  Calculator Here:
                  Thermal resistance calculator | MustCalculate
                  Cheers,
                  Ian

                  Comment


                  • #10
                    Too much filter capacitance can cause a transformer to overheat because the RMS secondary (and thus the primary) current is too high for what the amp needs. Transformers are usually rated for DC output current at a certain temperature rise, but the assumption is made that the filter capacitance is reasonable. If the capacitance is higher, the current must be derated for the same temperature rise.
                    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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