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Thread: Transformer Hum

  1. #1
    Senior Member Menschenstimme's Avatar
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    Transformer Hum



    Realizing that this is an oscure issue, here goes anyway. It regards the Peterson AC power console control unit. We have two at church (one in each console) and now I have one at home in my residence console. While this is an excellent unit, it has an internal transformer that hums constantly. Petersons advises that some hum more than others. Of the two at church, one hums so quietly that it is virtually inaudible. The other one is loud enough that if you are standing near the console in a very quiet church, the hum is obvious. Mine at home is between these two, hum-wise.</P>


    Unfortunately, in a quiet residence, this can be very annoying if you are sitting quietly near the console reading the latest edition of The Tracker or whatever. The one in my console is even mounted on felt. This helps, but not enough. Has anyone here found a solution to this problem? Perhaps a replacement transformer that is quieter? I am thinking of maybe even an external AC/DC adapter. It is intersting to note, that while AC/DC adapters do hum; I have never encountered one that is literally audible in a very quiet room.</P>


    Side note: I once had to replace my house's door-bell transformer because it had an intrusive hum that could be heard from the attic. It was working fine - just too much hum. The new one is very quiet.</P>


    I suppose I should discuss this with Peterson and ask them for the spec's regarding a replacement. I am just hoping that another member of this Forum may have dealt with this already.</P>


    Thank you!</P>

  2. #2
    Senior Member geoelectro's Avatar
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    Re: Transformer Hum



    No direct experience but... some transformer hum loudly because of loose lamanents or case parts. It might help by tightening all the screws on it.</p>

    Geoelectro
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  3. #3
    Junior Member adhall's Avatar
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    Re: Transformer Hum



    Menschenstimme:</p>

    If you are still in the mood to replace the transformer(s), you might try a "toroidal transformer". I have worked with equipment using this type of device and have never noticed any hum. Digikey and Mouser both stock a selection of them. A warning: You will find them to be more expensive than a conventional transformer of the same ratings.</p>

    Here is a link to an example:</p>

    http://www.mouser.com/ProductDetail/Triad-Magnetics/VPT24-2080/?qs=sGAEpiMZZMtlKt%2fhwW%252bxLShKYyyYbCyA</p>

    (Of course, this is probably not suitable as I have no idea what voltage and current ratings you are looking for.)</p>

    Best regards,</p>

    Andy Hall</p>

    </p>
    Allen TC-3S, Rodgers 321, Rodgers 990

  4. #4
    Senior Member jkrusel's Avatar
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    Re: Transformer Hum

    [quote user="geoelectro"]

    No direct experience but... some transformer hum loudly because of loose lamanents or case parts. It might help by tightening all the screws on it.</p>

    Geoelectro
    </p>

    [/quote]</p>

    </p>

    Loose laminations are often a result of marginal original design. Also, if the instrument is getting old and the filter capacitors in the power supply are going bad, the additional load on the transformer just as a result of the capacitors can cause it to start to hum, even if it's not overloaded (yet!). </p>

    </p>

    A typical operating temperature range for power transformers has a top end of about 55C. A very cheap and dirty way to measure that is to hold on to the transformer after it has had a chance to warm up. If you can't hold on to it for more than 5 seconds, it's over 55C, and probably being overloaded.
    </p>
    Jerry in Leslie, spinning around trying to find my way

    1990 Korg M1 - moved on to a new life
    1981 Lowrey MX-1 - giant box of bad connections
    1975 Lowrey TGS - gathering dust
    1973 Hammond T-524C w/mods - fun machine!
    1972 Hammond XTP - moved on
    1971 Gulbransen Premiere PR (1154) - awesome sound!
    1965 Hammond E-133 w/mods - her name is Emmanuele, and we are in love

  5. #5
    Senior Member Menschenstimme's Avatar
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    Re: Transformer Hum



    Thank you all for your responses. Please keep in mind that the unit in question is new and that the power transformer is to power relays that switch voltage on and off. The transformer is not part of any audio system. Moreover, I would not mind paying a relatively high price for a replacement transformer if doing so will eliminate the hum.</P>


    Thanks again!</P>

  6. #6
    Junior Member kcbooboo's Avatar
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    Re: Transformer Hum



    If the transformer is mounted to a metal chassis or other flat object larger than itself, this can act as a sound amplifier and turn the whole thing into a loudspeaker. A common trick is to mount the transformer on rubber isolators or even use rubber grommets on the mounting screws, so you separate the vibration from anything that would tend to amplify it. If the wires are long enough, this should be easy to do. If not, tighten all the mounting hardware. If there's room, you might be able to add a plastic stiffener between the transformer and a nearby solid support (console frame, for example) to reduce the ability of the chassis to vibrate. The solution depends on the mechanical installation of the transformer.</P>


    Bob M.</P>

  7. #7
    Senior Member Menschenstimme's Avatar
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    Re: Transformer Hum

    [quote user="kcbooboo"]


    If the transformer is mounted to a metal chassis or other flat object larger than itself, this can act as a sound amplifier and turn the whole thing into a loudspeaker. A common trick is to mount the transformer on rubber isolators or even use rubber grommets on the mounting screws, so you separate the vibration from anything that would tend to amplify it. If the wires are long enough, this should be easy to do. If not, tighten all the mounting hardware. If there's room, you might be able to add a plastic stiffener between the transformer and a nearby solid support (console frame, for example) to reduce the ability of the chassis to vibrate. The solution depends on the mechanical installation of the transformer.</P>


    Bob M.</P>


    [/quote]</P>


    I just talked with Peterson and by a fortunate coincidence they have just come up with a solution for the hum. They do indeed isolate the transformer somewhat assuggested. However, theyexplained to me that it is more of a magnetic isolation than mechanical. I do not understand the physics involved, but apparently rather than the transformer physically humming and transferring said hum to the case of the unit, it is happening magnetically.</P>


    They are taking care of this at no cost to me - not even shipping. I told them how ironic it was that I probably got one of their last humming units right before they figured out how to eliminate it.</P>


    At least this story has a happy ending!</P>

  8. #8
    Senior Member jkrusel's Avatar
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    Re: Transformer Hum



    I'm glad the factory settled this one for you.</p>

    </p>

    As to the physics involved, transformers rely on rather large magnetic fields in order to do their thing. Large magnetic fields can induce a signal into adjacent circuitry, through the wiring for example, so that the AC component of the transformer (in this case a 60 Hz AC current) can appear on the circuit and produce a 60 Hz hum. Take a portable AM radio and put it close to your TV and you will see a perfect example of induced "noise" from magnetic fields.
    </p>

    </p>

    </p>
    Jerry in Leslie, spinning around trying to find my way

    1990 Korg M1 - moved on to a new life
    1981 Lowrey MX-1 - giant box of bad connections
    1975 Lowrey TGS - gathering dust
    1973 Hammond T-524C w/mods - fun machine!
    1972 Hammond XTP - moved on
    1971 Gulbransen Premiere PR (1154) - awesome sound!
    1965 Hammond E-133 w/mods - her name is Emmanuele, and we are in love

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