…built a power supply…

So, I finally finished the bicycle I was rebuilding, cleared some workbench space, and gutted a 300W power supply out of an old Antec computer case. I then converted it to a power supply for my Yaesu FT-7800R ham radio, to use as a base station in my garage.

This is a 300W switched power supply that supports 10A on the +12VDC rail.

Then I removed the cover.

Then clipped the unecessary wires and taped them off. The only one’s I needed for the ham radio power supply was the yellow (+12VDC), the black (ground), and the green (power on). I kept 1 green, 3 yellow, and 4 black.

You can twist the green and one of the black wires together. Be sure to tape them up and shrink wrap them. Also, tape the ends of all the clipped wires (just to be safe).

Then twist the 3 black wires together, and the 3 yellow wires together, and crimp an Anderson Power Pole connector on each.

You should have a pretty clean looking setup at this point.

Now, reinstall the cover, and you’re done!

33 comments so far

  1. Thor on

    Nice project, I like it. Wire 25 together in parallel and make a 12VDC welder !!!!


  2. bloodhound on


    Welder? I do have a second identical power supply…

  3. jnadeau06 on

    Congrats on your new Radio. I also just ordered a new mobile VHF. I’ve never had a mobile (just handhelds) and therefor not sure how i’m going to power it yet. I am thinking about converting a PC power supply, but the mobile unit says it needs 13.8 volts, would I be correct in assuming it won’t work since the PC power supply supplies 12 volts ????
    Also, as far as your Solar Comment, I’ve been doing lots of research on solar power. Solar Panels are still VERY expensive. (About $4.50 per Watt you need to generate, so a 100 watt panel = $450, roughly) still very expensive … 😦
    I’ve written a few blogs on solar power at techienation.com …

    Jason, VE2RIF

    • Dr. Stephen Wilson, XE1UFO -- KA5SUT on

      Jason: There are many places you can buy solar panels much cheeper than what you quote. Let me suggest you study this guy for your solar project. He is in a solar-powered RV, but the principles are the same. http://handybobsolar.wordpress.com/

  4. bloodhound on

    You’ll like the FT-2800. Great little radio, and indestructible! The thing is built solid.

    I had contacted Yaesu concerning operating voltages and current draw. The response is that the mobile radios have a voltage operating range of 11.7 to 15.8 VDC.

    So, I built my power supply (ok, converted) and it registered 11.4 VDC. Apparently there are differences between voltage supply at rest, and voltage supply under load.

    Well, I hooked up my FT-7800R and it worked just fine with 11.4 VDC. So, a little less than 12 VDC is fine.

    I’m currently thinking of converting another power supply. There are also 3 VDC leads in there. If I can figure out how to connect them in series with the 12 VDC leads, that would give me a 15 VDC connection, which (using the same percentage drop) should leave me with 14.25 VDC. But, smaller projects are in the way before I tackle that one.

    Thanks for the link to the solar stuff. Great blog. My wife has been talking to me about straw bale houses for several months now, but I didn’t see what they were until your site. That solar install looked like a bit of work.

    73’s! Jason, WH7DA

  5. jnadeau06 on

    Thanks Jason for the great information !
    I did some research, and apparently if you want to add your 3 VDC to the 12 VDC in series, you’ll need to use a totally separate power supply. (Since all the blacks are grounded together)

    I just finished converting one of my power supplies as per the instructions on your blog. I get 11.66 volts with no load. Might be a close call. 🙂 Can’t wait for my radio to come in to try it ! 🙂

    73’s from Jason, VE2RIF !

  6. […] The dirt-simple project is documented, complete with step-by-step photographs, on his blog. […]

  7. WH7NB on

    Have been Using a Power Supply for LCD Panel for a while, 12v 5A, cost $35 EBAY,

    Good Luck WH7NB

  8. Phil on

    Another good use for old computer power supplies are to power stereo amps made for automobile use. I did this to power a subwoofer and it worked great… it’s a lot cheaper than buying those dedicated 115 AC to 12.0 DC power supplies.

  9. Randy Brooks on

    I just bought a used FT-7800R and I have a spare computer power supply that I’ll convert like yours. Is the reason you used 3 yellow and 3 black wires is so there’s more wire surface to crimp onto with the Anderson Power Pole connectors? Just want to make sure before I proceed. Also, what size Power Pole connector did you use?

    • LEE on

      if i use them for HT i do 3 plugs but for mobiles i use all 3 wires as shown..

      I easy way to think of it. would you prefer to water you garden with 1/8 inch line or 1/2 line…

      Bigger the line more the power of distribution.( lowers the chance of heatin up the wires.)

  10. Luis Cabrera on

    I was considering building my own power supply, but a fellow ham suggested I get one with at least 30 Amps of output… so I guess I will not be building one from a PC power supply (Apparently that provides only about 10 amps).

    • LEE on

      Not all of these PC power supplys provide just 10 amps .Many will go up to 16 amps and even a few others will go up to 22 amps.

      And the ham friend who sudjested 30 amp was he looking at your needs for a HF rig or justa simple HT and mobile radios…It simple to decide just look at you owners manual and check the spec’s of power needed and amp needed.

  11. james mott on

    I have a “Power Up! Model No; PU5500, 550 W, 32A +12 so there are 32A ATX power supplys. May use this conversion, thats what I got it for. The factory built ones are so expencive. I should get another one ang then have a 60A ps that i can use for about anything.

    • LEE on

      if it works and works under your usage and requirement .Why not get another .I would….

  12. james mott on

    Also I’ve found on other instruction pages to use a load resistor on +5V to keep more voltage at rest.

    • Bob Lunsford — KK5R on

      I use a 10Ohm, 10W resistor for this. NOTE: IT GETS HOT!

  13. […] 300w Power Supply wh7da.wordpress.com […]

  14. LEE on

    This a great project .We use these pwr supplys as this on each repeater in maine.on the Kq1l system its fabulous. Now some one replied about a 30 amp.Well any HF radio that might be useing at 100 watts well thats a no brainer use a battery or more wattage on the transformer. but as for HT, and mobile 2 m, 220,440,6m, 10m radios if you look at your radio spec”s youll see the 5-15 watts supplys will do majority of the needs with no problem.
    And just think they also make a great battery charger.And if you happen to make a DIY for a simple controller it can be a trickle charger.Most all HAMFEST for years now i find them for 1 thru 10 bucks is it worth it…..???
    YES……Being a HAM is studying the ART of Amatuer Radio. o yes before I forget I’ve have one the lites up a string of xmas lites low powered ones i found . And on your workbench yes great item for trouble shooting……..THE IDEAS is endless with this inexpensive project thank you for sHareing this……..


  15. Bill on

    Instructables.com has all kinds of hacks that are useful in ‘Da Shack’.

  16. Phil on

    I recently read a blog about this conversion where they disconected the regulated 5v bypased the regulator and introduced the 12v line which then regulated up to 14v with the addition of small variable resistor, it all looked very easy and made sense to regulate the needed12V rather than the unrequired 5v, it is on the internet somewhere use google.

  17. Leon Eady Jr on


    What size/model # connectors did you use?

  18. Mildred on

    Heey there! I’m at work surfing around your blog from mmy new aople iphone!
    Just wantyed to saay I love reading your bloog and look
    forward tto alll youur posts! Keeep up the excllent work!

  19. Christopher Rose on

    I am quite impressed. I just bought a Kenwood TS430-S that has a voltage requirement of 13.8VDC at 20 Amps. I wonder if this would work to power it up and use it, albeit not at maximum output. I will have to check the garage and see what I have. I like this idea. Cheaper than buying an Astron on ebay.

  20. Gabe Fries on

    If you are looking for a computer power supply with more amperage to use in this project, I would suggest a model that I have just purchased for my computer. It will supply 62Amps @ +12v and 25Amps @ +3.3v and +5v. It is a 750 watt ATX style. Corsair CX750 Builder series. Also it is rated 80 Plus Bronze, which means it is up to 85% efficient to reduce power usage, heat generation, and noise levels. It has a thermally regulated fan. And while I have seen them go for $120 at a lot of retailers, I got it on Amazon for $69.00 and free shipping. Which is a whole heck of a lot cheaper than any other 60 amp regulated power supply your gonna find dedicated for this type of purpose. I bought a 33 amp 12 volt switching power supply off Ebay for $60 before I thought or read about converting one this way. It works great, but if I had read this sooner, I might have done this project with this type of power supply. Anyways just a tip for anyone interested.

  21. Nigel A. Gunn on

    On many of those computer supplies, you NEED a load on the +5V supply (try half an amp or so) to get it to regulate properly. Only the 5V supply is regulated and the others track it.

  22. Phil on

    For those looking for 30 to 40A try finding an old server power supply these can go up to 13v 50A no messing with load resistors just select your output contact plates and wire up, some even have a variable power adjustment pot near the contacts so you can turn up to 13.8v.

  23. John on

    what do you do with the green wire (power on) I have one similar and the green wire goes to a auto light bulb for the supply to detect a draw, when you turn the supply on the light bulb turns on and allows the supply to activate??

  24. John on

    forgot to add this info is all over youtube as well.

  25. TechGazette on

    How well does this work though? I feel like the current would be unstable or
    really susceptible to a short or something.

    • Chief on

      Why do you feel it would be unstable? That doesn’t make any sense. It’s no less stable than it was when it was a stable power supply for a large computer with a three hard-drive raid array. How would it be susceptible to a short?

  26. NoCrud on

    I have converted several of them and I find that if they do not start when you power them up, you have to connect the white wire to ground. Also, there is a remote/load sense wire that sees the output line voltage and adjusts it up if the load is heavy. However, this line is to make sure that the load stays at a constant voltage level with current surges. With this in mind, if you make a voltage divider across the output lines (Yellow-Black) with the center lead going to the remote voltage sense wire, THEORETICALLY it cold be adjusted to make the power supply think it is running too low a voltage on the output and therefore jack up the voltage. This is something to try but also keep in mind that if the voltage is higher, the current drain can also be higher so that 20A power supply might sense a higher current and shut down.

    I have used a 12V supply on my FT-450 when I sold the good one but cut the output power back to 50W so the current would stay within the limits of the computer supply. Same thing I did when I used a lawn mower battery on the rig, to make sure the current was kept down.

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