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Thread: AC phase correction caps ?

  1. #1
    Low Bitrate
    Join Date
    Jun 2000
    Massapequa, New York, USA

    Post AC phase correction caps ?

    On this page I read that if you remove the AC phase correction caps on the powersupply it will eliminate the humming sound in your speakers. Does anyone know if this works ?

  2. #2
    Raw Wave wizardPC's Avatar
    Join Date
    Jun 2000


    That guy isnt the only one to claim that it works, and I'll prolly do that when I put my system in (no, Aaron, its not permanant). the only thing is that there are 2 of those "square" capacitors on my PSU. dont know which one to take off
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  3. #3
    Bj is offline
    Variable Bitrate
    Join Date
    Aug 2000
    Perth W.A Australia


    Well I know it works

    By removing the phase correction caps, you give the inverter an easier time driving the PSU.

    The Theory:

    You see, an ATX or AT PSU is basically a squarewave device itself, just it runs at a higher frequency. The AC is taken in, then rectified (converted to DC) so you have 240V (approx) or 110V DC, that is then switched via another chopper transistor that drives a HF transformer at a frequency of around 20khz. This is then taken off the tranformer and rectified again with much lower ripple, (due to the high frequency only one diode is needed instead of 4 (full wave)) to convert it to smooth DC. And then you get your lower voltages from here ie 5V 12V etc.

    What I'm getting at here, is that your inverter doesn't need to have a pure sinewave output to begin with. If you remove the AC filtercaps, chokes, and MOV's (blue surgy things) you can drive the supply with a squarewave input. It doesn't care if it's smooth or not, because it becomes DC once it enters the supply.

    So what it means to you, is that you can have a squeaky clean power supply from an inverter, just by performing a little surgery on the input of the PSU. Mind you it does bite! Don't perform this mod with the inverter on! Basically remove anything that is in parallel and series with the mains supply UP TO THE BRIDGE RECTIFER (Black square thing). So in the end, you are connecting the inverter output directly to the rectifier.

    I gather only you "experienced" people sould try this, but if you don't know one end of a circuit board from the other, I suggest just removing the big square caps near the supply input. This is easy as you only have to unsolder them. No wires need to be soldered in their place! Just remove them.

    This will give your system a major lift in efficiency, but if you want to go the "whole hog" and remove everything, that would be better. But only do this if you feel you can.
    Yes it does work. I have three working sweetly for years.

    ps my site has frames, so go to it from here then go to projects/car mp3 player/ power supply

    Hope this helps you guys out who were wondering.....

    BjBlaster! Car MP3 & Carputer!

    "The solution to one problem is only the beginning of another"


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