I am new to electronics but have a general understanding. I would like to modify a ATX power supply to get about 14 volts from it. I've heard that I need to use diodes to acheive this, but I don't know where to put them. Any help would be greatly appreciated.
The diode method you've mentioned probably means that you have to attach the diodes to the ground, reference pin, of the 12v regulator but that would increase the voltage of your whole 12v rail. What you could do is either build a DC voltage converter or obtain a variable switching step-up regulator. The main reason you can not attach another 12v regulator onto your 12v rail and step the voltage up that way is because linear voltage regulators are meant to break voltage down to a stipulated parameter and the rest is dissipated as heat.
There's a method described here but it's certainly not for newbies. More of a build a 13.8v psu using parts from an ATX one.
My PS uses a TL494 chip, since a diode has a voltage drop of about .7V, couldn't I put 2 or 3 diodes in series between the IC and the circuit board? I just need to know which pin is monitoring the output.
Yes you could do that but the main thing that is holding you back is the fact that you will be raising your 12v rail over the specifications of some of the hardware in your computer. Unless you are utilizing another PSU for your system I would not advise it.
That's fine-I'm not going to use that PS in a PC. So can anyone tell how to modify it that way? Thanks.
In that case go right ahead, this website contains the data file on the chip. Looks like pin 14 is your voltage reference pin. It is a switching regulator so I'm not entirely too sure on the use of diodes to change the voltage output, someone else with knowledge of this type of regulator would be better to talk to.
i think you should just get a DC-DC converter as sold here you get 2 for a dollar, and you can use them for other things if you need, say, -12 volts hehehe (my use) although they dont run stable unless you hook up the proper capacitors and stuff shown on the data sheet.
I was able to get 13.8V out of it by changing the resistor that goes between pin#1 of the IC and the 12V output.
could you please explain in great detail on where i put the diodes i don't mind increasing the voltage of my whole 12v rail i dont plan on using the power supply on my pc
Have a look at the motherboard plug of your psu, and you'll notice that on one of the yellow 12v wires, there is also a thinner yellow wire connected to it at the plug. This thin yellow wire is the 12v voltage sensing wire, so no need to open the psu, you can just cut the thin wire, and solder in one or more diodes, or preferably a variable resistor, so you can let the psu sense less volts that what there is, which bumps up the voltage. I've only done this using variable resistors, around 1k, 2k, 5k, that way you can easily fine tune the voltage. 14v shouldn't be a problem, you'll know if the psu is being stressed, as you'll feel the heat and hear the fan spinning faster. Just make sure you turn on the psu with the resistor set to about 0 ohms, then slowly increase the resistance, whilst measuring the output with a multimeter, and have the desired load connected. If you turn on the psu with the resistance at maximum, the psu might not start or possibly overload itself The wattage of the psu remains the same, so bumping up the voltage will lower the available current. If for example your psu has a 10a 12v rail = 120w, bumping up the voltage to 14v would mean the new maximum current would be 120w/14v = 8.6a. All the standard precautions apply, like balancing the load on the rails, and not expecting the psu to continuously deliver anywhere near it's rated maximum loads, especially when using a cheap psu!
