1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Convert PC Power Supply for C.B use?

Discussion in 'Home Brew' started by T23, Oct 18, 2010.

  1. T23

    T23 Active Member

    Joined:
    Apr 17, 2010
    Messages:
    645
    Likes Received:
    10
    I m looking at converting a PC power supply to use for a C.B, does anyone have any information?





    T23
     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,613
    Likes Received:
    10,400
  3. office888

    office888 Active Member

    Joined:
    Jun 8, 2009
    Messages:
    499
    Likes Received:
    16
    They're 12v, not 13.8v.

    Also, switching power supplies are known to produce RFI.

    Good luck!
     
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,613
    Likes Received:
    10,400

    Generally you can raise the 12 volts up to at least 13 volts but the noise is still a factor to deal with. I was contemplating using a gang of switching PC supplies to make a 40-50 volt supply to power some MFR-151G 300 watt power modules I have but the thoughts of trying to cure all that RFI scared me back to my senses. :unsure:
     
  5. hookuspookus

    hookuspookus Member

    Joined:
    Oct 8, 2010
    Messages:
    4
    Likes Received:
    0
    has anyone told you how to do it ? i'm interested in doing this also 5 A of clean filtered power
     
  6. T23

    T23 Active Member

    Joined:
    Apr 17, 2010
    Messages:
    645
    Likes Received:
    10
    Yeah, I figured it out PM me for details these things are rock soild when conversion is done, you can get one of those alternator hum cancelers to cut the noise out.


    T23
     
  7. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,736
    Likes Received:
    3,115
    I have had relatively good luck doing this also. Seems most computer power supplies are not too noisy. Sometimes you will find one that puts a noise level in your receiver. I can tell you from experience an alternator whine filter will not get rid of noise from a switching power supply. Unlike in the case of the alternator where we want to filter out relatively low frequency AC ripple, the switching supply creates RF hash. This RF is actually radiated from the power supply circuits and is not easily filtered out. It's usually picked up by the antenna and removing it will confirm it's radiated RF and not ripple on the DC line.
     
  8. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,613
    Likes Received:
    10,400
    Agreed. The noise from a switching power supply is not simply a high pitched whine superimposed on the DC voltage but rather a true wideband RF signal that is radiated out into the air.
     
  9. T23

    T23 Active Member

    Joined:
    Apr 17, 2010
    Messages:
    645
    Likes Received:
    10
    Good points... Maby extra power supply case shielding? there not very good stock.

    They got so many holes in them I aint surprised they have RF noise.


    T23
     
  10. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,613
    Likes Received:
    10,400
    The holes are not too big of a deal as they are quite small as compared to the size of the wavelength involved and aren't that much different than the vent holes in other RF related gear. The big problem is that none of the wires are RF bypassed and the signal basically uses them as transmitting antennas and radiates all over the place. Extra shielding would help but the wires need to be bypassed as well.
     
  11. sp5it

    sp5it Master of puppets

    Joined:
    Jul 9, 2009
    Messages:
    1,880
    Likes Received:
    2,061
    Better use 203W Xbox power supply. Cheap and good filtered. It's working like charm.
    Mike.
     
  12. KJ6HYC

    KJ6HYC Member

    Joined:
    Sep 27, 2010
    Messages:
    31
    Likes Received:
    3
    I would think the computer PS would work well, as a computer needs good clean DC to function. The computer PS is a switcher type and the switcher's frequency S/B above the human audio range. The only drawback is the 12V vs 13.7V. You should be able to adjust the voltage by changing the resistive divider, or adding a silicone diode in series with the sensing voltage pick off in the +5V side of the PS. The +5V is the only voltage that they regulate, the 12V and the rest follow the +5V. Be carefull the PS has high voltage (as high as 340VDC via a voltage doubler with capacitor storage), can be lethal!
     
  13. T23

    T23 Active Member

    Joined:
    Apr 17, 2010
    Messages:
    645
    Likes Received:
    10
    Thanx for that Xbox Power Supply idea man... I forgot I had an old one of those, it should be perect for my HTX-100...


    T23
     
  14. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,613
    Likes Received:
    10,400
    Typical switch frequencies are around 15-30 KHz depending on the power supply and load. Not all PC PSU's are bad and even the ones that are bad do not have dirty power on thier lines. As stated before, most of the noise is generated as RF and the computer still sees clean power on the supply rails. I can take a handheld scanner or HT and program it to receive AM mode and hear all kinds of noise when I wave it near my computer but the computer works fine.
     
  15. T23

    T23 Active Member

    Joined:
    Apr 17, 2010
    Messages:
    645
    Likes Received:
    10
    Is there a way to tell the amperage that I am putting out on a converted supply without standard equipment?


    T23
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!