Bench Power Supply From ATX - Page 1
Forum section: electronics / beginners

author: Samyaza
author_rank: Contributor
timestamp: April 09, 2016, 07:42:56 am
content: Hello, I'm new to electronics. I own two compaq ATX power supply to be specific the: Compaq ps-5201-4t2.I tried to find schematics on the web but without success.It has a 20 pin P1 connector. I tried to use a generic pinout for a general ATX power supply but is not starting without the mo-bo connected.I thought it needs some loads, so I used 10 Ohm 5W resistors on 12v and 5v rails. Still nothing.I also tried to put such load on the 3,3 V rail from the P1.As I said the colours of the wires are different, but I tried them by analogy.Whatever I do, I can't start the power supply. Any ideas?I'm quite disperate. I want to use it to make a bench power supply.Can anybody tell me the pin configuration of the 20 pin compaq PS-5201-4T2?I've seen they are using separate colour form a standard 2o pin ATX power supply.They are the same pins but with different colours?Where should I put loads to start it without the mo-bo?Thanks!

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 09, 2016, 10:58:32 am
content: http://i155.photobucket.com/albums/s318/paulpsomiadis/compaq_psu_atx_mod_no2_improved.jpgYou need to ground the PS_ON# to turn it on.

author: Samyaza
author_rank: Contributor
timestamp: April 09, 2016, 08:29:42 pm
content: I grounded the PS_ON but is not starting.Also I tried to use 10 Ohm 5W resistors as load on some rails, like the +5 +3,3 +12 and nothing.Other ideas?

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 09, 2016, 11:19:01 pm
content: Can you measure voltage on the 5V AUX line?

author: Samyaza
author_rank: Contributor
timestamp: April 10, 2016, 08:17:50 pm
content: nope is not working.. is 0

author: prawncrackers
author_rank: Contributor
timestamp: April 11, 2016, 07:22:04 am
content: maybe its damaged? why dont you post pics of the board and maybe we can find the fault if it is damaged.btw some ATX PSUs have ATX-specific controller ICs which monitor the 3.3v 5v and 12v outputs and will report a fault if the voltages arent right in all 3 pins. that makes it hard to modify the output voltage. ATX PSUs with TL494 ICs are easily modifiable.

author: Samyaza
author_rank: Contributor
timestamp: April 11, 2016, 08:23:42 am
content: No is not damaged.. I have two of them and both have the same problem. Is the only atx source model I couldn't start without mobo!I need to find a way. I want them to make a power bench power supply. I need like two of them. One made from an ATX power supply and another made from a switch mode power supply 24V and 10 Amps. For the other is a little bit complicated with the voltage control and current limiter.The problem is the LM317 is not working over 2-3Amps, the LT1038 is obsolete and nowhere to be found so I went over this schematic:http://electronics-diy.com/electronic_schematic.php?id=981This solves the voltage regulation but... I idon't know what to do about the current limiting.I need a knob to fix the maximum current for an app and for both of them of course I'll have displays, actually a voltmeter and an ampermeter. The LCD type. In fact I found a nice combo. 0 to 100V cc and 0 to 10Amps in the same enclosure. neat..

author: Grayfox
author_rank: Regular Contributor
timestamp: April 11, 2016, 08:25:01 am
content: The wire you are grounding is green PS_ON right?Not the gray PWR_OKTry connecting the PWR OK to a red LED with a 220ohm .5w resistor to add some load to itThink I read that the PWR OK needs to get some kind of signal to keep the PSU on, I know it tells the mainboard that the power output is fine.Also you said this is a compaq PSUSaw this so your pinouts may not be to the ATX spec

author: Samyaza
author_rank: Contributor
timestamp: April 12, 2016, 06:12:50 am
content: is a 20 pin P1 not 24. I will try today with the power ok wire.

author: Grayfox
author_rank: Regular Contributor
timestamp: April 12, 2016, 07:01:43 am
content: Quote from: Samyaza on April 12, 2016, 06:12:50 amThe other 4 pins are+12v, +5v3.3v, GNDPin 14 is PSU_ON in both 20 and 24 pin ATX connectorsIt is a wild shot by try connecting the PWR OK to PS_ON#It might turn on, but I wouldnt rely on this for long term, but doing it for a second should be fine.