I have used a 650 watt computer P.S. for many purposes with no real problems other than having to: 1) Filter & Shield for the RFI that it generates 2) Put a resistor load on one of the outputs so that the thing would be stable (as mentioned in an earlier email).
But I think the best solution is the old-fashioned linear supply: Take a big, (say 450 watt) and free UPS transformer and apply 120 VAC to its 120v side. Rectify the output using a sturdy bridge rectifier and filter it well. The output will be about 12v x 1.414 = ~16 volts which will feed a low-dropout regulator chip. Run this ~16v output into a 12 volt regulator chip (or a variable voltage one) that is placed above ground to deliver 12 - 15 volts (adjustable, using a pot). Use pass transistors in the negative rather than the positive lead - these can be bolted right to a heavy chassis used as a heat sink. Here's a good reference for doing this: http://www.qsl.net/wb4kdi/PowerSupply/UpsideDown.html Derate the 450 (or larger) watt UPS transformer by about 1/3 as they are not intended for long periods of use. Mine powers a 100 watt Yaesu without getting hot. Add a $5 Chinese digital voltmeter from eBay - makes a very nice output indicator. Bend your own aluminum case or put it in a metal UPS case. Or a wood case with Masonite panel. Or breadboard it and keep the cat away from it. Others can make a good case for the switching supply but I find them hard to repair if a unique component fails. My linear supply is built of junk I found in recycle yards - total cost is about $15, mostly for a good can of spray paint and the voltmeter. On the other hand, computer P.S. can often be had free, are small and don't need much modification other than changing a resistor (sometimes a variable one) to raise the voltage. Lots of articles on the internet about using computer p.s. Frank W4NPN On Wed, Nov 30, 2016 at 11:03 PM, Alex [Temple Boatanchors] < [email protected]> wrote: > ATX PC power supplies are very inexpensive ($20-$30), highly efficient and > very lightweight, and basically use the same concept as those modern > lightweight "wall-wart" wall transformers. But due to their switch-mode > nature they generate a great deal of RFI in the HF regions, specially the > lower frequencies bellow 10-15MHz or so, but should be fine for use with > gear on 6M, VHF, UHF and up. The level of RFI perceived in the receiver > much depends on how well the radio itself and coax to the antenna is > shielded and grounded, and the distance between the gear and power supply > is a factor as well. Also, the output is 12V, not the required/desired > 13.8V that most mobile DC operation gear needs to attain full output power. > But with small modifications by changing one or more resistors (varies from > model to model), in most cases one can "fool" the regulator to raise the > voltage as needed without tripping the protection circuit. Another issue is > that the power supply usually requires a minimum load on one or more of its > outputs for stable operation of the regulator circuit, as one or more of > these outputs are used as a reference voltage. A resistor or appropriate > incandescent light bulb might do the trick as a load. > > I use a 700W ATX power supply that I modified for 14.4V output to manually > charge a 150Ah lead-acid backup battery bank. It easily will charge it at > 20-25Amps and generates minimum heat as long as its internal fan is > running. Basically these power supplies can be used as very inexpensive > power sources or charger. But while charging it basically wipes out my > reception on 80 and 40 meters. Then again the internal power supply of my > nearby Apple TV does pretty much the same, only at a lesser degree than the > charger. > > Just search for "ATX power supply modification", there is quite a bit of > info out there. > > > > At 07:17 PM 11/30/2016, you wrote: > >> OK gang .. Can someone provide a definitive answer to this question? >> I see all kinds of conflicting opinions and would like to know what the >> thinking is here. Or, if someone here is using them for that purpose. >> >> >> Computer power supplies. Can they or can they not be used to power ham >> rigs such as two meter rigs, or even >> >> low power HF rigs? >> > > > _______________________________________________ > Boatanchors mailing list > [email protected] > https://puck.nether.net/mailman/listinfo/boatanchors > > -- Frank Barnes W4NPN Chapel Hill, NC Grid Square FM05 Cell 919.260.7955 _______________________________________________ Boatanchors mailing list [email protected] https://puck.nether.net/mailman/listinfo/boatanchors
