Cheap Shack Power Supply for under £10 or thereabouts!
A new PC Power Supply can be bought extremely cheaply these days. If you look for a 450w ATX power supply, it should give you 20A output, covering the needs of your average HF transceiver. However there are some catches! You’ll only get 12v out of it and not 13.8v. In my scenario, my 2m linear puts out 85% of the power that it would if I had that extra 1.8v. So it depends on the situation whether that’s a problem or not.
I have a ‘proper’ PSU for the main station and the ‘cheap’ option for a second station in a more accessible part of the house (see pic below). The stealth station is hidden in a drawer in the dining room! I use a 350w ATX PSU to power both a 2m Icom IC-2E transceiver and a Mirage B-108 2m linear. The IC-2E only puts out about 1.5w which gives 12w out of the linear. I bought my power supply from CCL in Tong, Bradford for about £8.
Below you can see the ‘stealth shack’ and the ATX power supply fixed on a shelf at the back of the drawers with the modifications described further below.
Click on the link below and read the original article from the Wikihow site but the key info is:-
yellow cables are +12v (high power)
red cables are +5v (2A) – except for the fan which is usually 12v
black cables are 0v
An ATX PSU requires the power sense cable to be connected to ground before you get any volts out, so find a way of permanently connecting green to black.
The second catch is that you might find that the PSU has got less than adequate RF filtering in the mains supply line. If you find you don’t have the filtering in yours, you will be hearing a lot of noise on 160m and 80m whenever the PSU is plugged into the mains (it doesn’t have to be doing anything).
If you’re wanting to run HF equipment then you need to look for two things:-
1. look for an RF Mains Filter at a rally – they look like the two on the left in the pic below.
2. look for an ATX supply with an output mains socket as well as mains input socket, like the one on the right in the pic below.
You need the outbound mains socket because it is generally the same size as the RF Filter you’re going to fit in it’s place and throw away that outbound socket. Fit the Filter in the outbound socket position and disconnect the old mains input socket. When you first open the ATX, pay attention to the way live and neutral get swapped over between the input and output sockets and DON’T wire the RF Filter like the output socket was! The RF Filter connections should look like the input socket connections used to – ie. from the rear of the front panel. Earth pin is upper most, live is to the left (possibly a white cable) and neutral is to the right (possibly a black cable).
Before but after I’d chopped off many of the extraneous cables
After – note that I wanted to change fan speed so I took off the A/C voltage switch and replaced it with a fan speed switch that powered the fan from either a 5v or 12v supply. This was later changed to either run the fan at 9v by a 40-ohm resistor from the 12v supply or at 12v without the resistor.
I got the idea from an article on the Wikihow site – How to Convert a Computer ATX Power Supply to a Lab Power Supply
DON’T WORK INSIDE THE PSU WHILE THE POWER SUPPLY IS PLUGGED IN TO THE MAINS!
ALSO BE CAREFUL NOT TO TOUCH THE LARGE CAPACITORS – REMEMBER THEY ARE LIVE, EVEN WHEN THE UNIT IS SWITCHED OFF!