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ASTRON RS-50A Noisy

Discussion in 'Ham Equipment' started by Se7en, Dec 13, 2011.

  1. Se7en

    Se7en Well-Known Member

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    It has CORK material padded between the huge transformer and the top Case. lately the power supply has gotten louder and louder......and yes when turning on in a cold start it kicks sometimes... which is normal from what i understand. i would like to quiet it down a bit any possible ideas how to quiet this thing down?​



     
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  2. Se7en

    Se7en Well-Known Member

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    This is in the wrong section can it be moved please.
     
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  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    Start by tightening every nut, bolt, and screw you can find especially the bolts holding the transformer to the case and the bolts holding the transformer itself together. Tighten them as tight as you can as the metal plates in the transformer often vibrate when loose and can be quite loud.
     
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  4. Se7en

    Se7en Well-Known Member

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    thank you.
    its a few db quieter still noisy but not as bad :)
     
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    Last edited: Dec 13, 2011
  5. Mudfoot

    Mudfoot Supporting Member

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    I have a big Tripp Lite that developed a bad power switch. Picked up a new switch and when I took the top off; I discovered that just about every screw and nut was loose.

    Tightened everything down with thread locker.

    Find some rubber padding or something to sit your supply on to help with dampening.
     
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  6. KM3F

    KM3F Active Member

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    If anyone is interested in why this conditon exists, here it is.
    It depends on where in the AC cycle you last turned the power off.
    This can leave the core magnetized.
    The next time it is powered up the core presents a very low impedence to the AC input and causes it to draw more than normal current along with charging the filter and pulls on the metal cabinet hard. This amplifies the noise and moves anything that will move and contributes to shortened switch life.
    This is why it does not happen every time.
    The solution believe it or not is 'soft start' just like an amplifier has.
    They are easy to make and install.
    A SPST relay with contact rateing of at least 10 amps and a 25 ohm 25 watt resistor wired for a second or less time delay before the full application of AC power to the primary winding, will quiet it down.
     
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  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    That takes care of the start up but sometimes they will hummmmmm like a bugger during standby and get worse under load. It is for the same reason, circulating magnetic currents in the transformer, and can generally be cured by tightening all the bolts and mounting the transformer on a piece of rubber between it and the chassis. The soft start is a good idea on bigger supplies and I have been meaning to install one in my 40 amp Tripplite but keep procrastinating. Several years ago I had to replace the filter capacitor bank and decided that the 100,000 uF can I had would be good. Man that beast thumps like a bugger when I turn it on. Start up current must be through the roof.
     
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  8. TonyV225

    TonyV225 Supporting Member

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    KM3F, You are correct as far as getting the massive inrush current thump taken care of and Ive actually seen older Palomar and other power supplies trip circuit breakers on power up. I understand what they are saying on the loud hum or vibration the supply is giving off.

    Its not in the radio recieve like a bad filter cap would do its simply the whole powered up power supply making noise. Ive heard some that almost sounded like they were going to explode. I have a 65 amp that popped one night years ago it was sitting at an idle and pow that was it. I opened in and replaced a few caps but it still didnt work and another forum memeber has it and didnt have time to look at it so Ill be getting it back to look at again.

    I remember when it happened I call triplite and they wouldnt repair it or sell parts but said " We will sell you a new one at a good deal" I thought it was a buncha horse $h!+. I remember mine also made a little noise a bit and I could never figure it out.
     
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  9. Se7en

    Se7en Well-Known Member

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    The powersupply site on the floor on a piece of marlble tile. It still hums. But it isn't a big deal now that its on the floor.

    Sent from Outerspace, on the DarkSide of X.
     
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  10. KM3F

    KM3F Active Member

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    Very often a hum after startup is the winding is loose on the core.
    In big commercial units there are wooden wedges used to tighen the winding.
    In smaller linear units the steel metal cabinet will modulate from the 60 hz magnetic field in the core being so close.
    So you can have at least 3 sources of noise all or any one or combination of them.
     
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