Which type of power supply?

Hi!

I'm planning to make a power supply for 0-20-30 volt and 5+ amps.

I found these to build projects

**broken link removed**

https://diyfan.blogspot.dk/2013/03/adjustable-lab-power-supply-take-two.html

But I thought that an easy way to get what I need is just put two atx psu in series and put a cheap voltage regulator from Ebay on them. But is there any disadvantage to using atx psu instead of one of the above projects?

I am not familiar with ATX PSUs, but the question is, I reckon the 5V would deliver 5Amps, but what about the others voltages. They are also fixed voltages, so how are you going to make them variable.
There is a good argument , that if you have the circuit diagram, you couls strip all the secondary windings and rewind just one to give you your 5A, The number of turns would give you the voltage, and then you would have to modify the mark/space ratio of the main inverter circuit to reduce the voltage.
It will not be quick or easy or cheap, but once you have done one , then subsequent units would be very cheap and quick to reproduce.
Starting from scratch a mains transformer, regulator chip and a some power transistors on a heatsink would get you up and running with a couple of days, not efficient electrically but very efficient in time !
Frank

I believe ATX supplies are not floating, so series connection does not work.

You can consider buying these. Adjustable Universal Chargers.

Ok, sounds like it is the better solution to make one than to use the atx.