Question on converted ATX power supply

I just finished building this power supply as shown in the video. I tested the power supply first to see if it was a good one. The fan went on so I figured ok, but after finishing the hookup , I turned the power on , the fan started but stayed on for only two seconds then off. Is the power still good or caput ??

@conlo This is probably a trivia suggestion but did you ground the green wire that makes sure the supply turns on?

@starnovice Yes I did

@Conlo Many ATX power supplies have a built in protection, where after switching on, it switches itself off shortly after if it doesn't detect any load on either of the rails. 

Make sure that before powering it on you hook up something that draws at least 50-100mA  (usually a 100-120mm fan would do the job. or maybe an old CD-ROM player or something like that.)

See if that makes any difference.

Posted by: @conlo

I just finished building this power supply as shown in the video. I tested the power supply first to see if it was a good one. The fan went on so I figured ok, but after finishing the hookup , I turned the power on , the fan started but stayed on for only two seconds then off. Is the power still good or caput ??

Did you measure all of the wires for proper voltages?  Sounds like you missed that step... (?)...

May help finding out what is wrong...  (?)

I am in the process of making one of these...

I got all of the PS wires together:  Only: BLK, RED, YEL, BLU, WHT, & Org).

I had all of the tips stripped & isolated for safety and proceeded to measure the Voltages. 

This is what I got:

RED ...  5.16 vdc OK

YEL ...  10.97 vdc Should be 12!  Is this close enough? Should take steps to boost it to 12?

BLU ... -10.23 Not going to use it...  BUT, is this supposed to be -12v?

WHT ...  -5  Not going to use it.

ORG ...  5.155 vdc  Is this the Standby VDC?  There is no provision for such switching.  ON is ON!

There is NOT any 3.3v!  I guess these were from real old computers! (?)

There is apparently NO NEED to have a Load resistor to make it work.

I just plugged it in and the fan ran and the voltages were as above.

I am planning on using Buck Booster on the 5v to get 3.3v as well as one for 6v.

I was planning on using Buck Booster on the 12v to get 9v... BUT, now that the 12 is really closer to 11v should I proceed to Buck Boost a 11v to get 9v??  (probably yes)  Should I use 11v as the 12v?

I have a rotary switch to select the meter input.

I am going to have terminals for:  3v, 5, 6, 9, & 12 vdc ( and switchable to meter)

I am also going to have a strip of five USB power points for another source of 5v and to Charge batteries, etc.

There is NOT a Power On Switch:  Should I switch just the White (neutral) 115VAC wire for Power On

Thank you for your help,

Joe Lyddon

Hi Joe

The odd voltages where you expected to get 12-volts makes me wonder about the state of the power supply, as you said it was an old one. 

Did you perhaps try measuring the voltages under load? The negative 12-volts usually isn't capable of much current as it was used only for the RS-232 (serial) ports, but the positive 12-volts on a computer supply is used for hard drive and CD -ROM motors and for fans, so it generally can source several amps.

If the voltage drops when you put a decent load (i.e a 10-ohm power resistor if you have one) on it then the supply probably has a few bad electrolytic capacitors, they tend to degrade over time and if your supply doesn't have a 3.3-volt output then it's likely a few decades old.

If it stays steady then it's probably just some components have gone out of tolerance. While there likely is an internal adjustment to fix it I'd be hesitant to suggest trying it without a proper schematic or service diagram, you'd also need to open the case and mess around in an area with some high voltages and currents.

Bottom line, determine if it still is a fully-functional device, or will you need to replace 15 capacitors to bring it back to life?

😎

Bill

@dronebot-workshop

Bill, Thank you for the reply!

It IS a few decades old...  20 yrs easy...

===========================

Detail Spec's:

HIPRO model HP-200PP3

DC OUT: 5vdc/20A  12v/8A

Fuse rating: 5A/250v  -5vdc/.5A   -12vdc/.5A

Max power output: 200W

Made in Thailand

===========================

It is super clean...  it has 2 electrolytics  not huge...  maybe 1" in dia. x 2-3" high.

I thought I'd wire-up the meter (like yours) and measure everything again to see what it looks like.

I will put it under load too like you suggested and see how it reacts...

Do you think 11v for the 12v is within useable range?

Thanks again...  will report my findings...

Have a good one!

@joelyddon

I would think you might find some items that might work at 11V, but most items that want 12V won't work at that low of a voltage.

My ATX puts out about 12.25 volts, even with a pretty good load.

@codecage

OK...  Very good...  I will check it out a little more... Under load...

It may turn out to be just plain JUNK after so many years!

Thank you!