From the land down under

Posted by: @wilky

Hey folks, Wilky here, came by this forum via youtube then the website and building an atx pc psu into a bench unit which did not work as such. Followed the instructions but am only getting 10+v off the 12v and 4+v off the 5v.

The power supply is a Foxconn HH-450EBTA and I have an 18ohm 10w resistor on the 5v side as per the instructions, any ideas greatly appreciated.

Is that 10V and 4V read directly off the Foxconn leads or off the output jacks from the front panel ?

@will what I have done is cut all but 3 12v side wires out, same with the ground and same with the 5v side plus used the resistor. On the 12v side I have a single plug to power up an lcd screen controller board and on the 5v side I connected a usb socket so I could run usb fans etc. I have measured the voltage from the cables and from the fittings and still get the same result.

Cheers Wilky

@wilky 

I can't find any diagrammatic representation of what power leads there are for the Foxconn HH-450EBTA. What I want to know is whether the observed voltages were measured from the ground and leads directly on the Foxconn.

In other words, if the voltages are wrong on the Foxconn, there's no future for the rest of the supply you're trying to make.

@will I have measured the V across the power and ground leads and the V from positive to ground on the case and on the board, all give me the same thing so yep I am figuring it might be good for the bin as well. Could be why the pc it was in stopped working as well. Thanks @will.

Cheers Wilky

@wilky 

Yeah, if that's the voltage at the source then it sounds like it's time to dig a hole for it 🙁

On the other hand, maybe it means that the PC can be restored to use with a new power unit.

@wilky Is it standard ATX cables?

@wilky Did you check each voltage across all 8 grounds, and while you are at it, make sure to test each voltage you care about, 5 x 5V, 2 x 12V, and a bunch of 3.3 that I don't think you are interested in. A bad main ground can explain low voltage, I would try finding that, follow each ground and case ground back to find some common point where there may be a loose or oxidized connector. Solution is tighten and/or clean/sand the connector.

@ronalex4203 yes but all the connectors and such have all gone in the bin. Not fussed if it doesn't work though, psu boxes are easily come by, in fact I was given a pc today and figured I would use the psu out of it but I have gotten the pc working and it runs a treat using a linux live usb os.

Cheers Wilky

@ronalex4203 ok ta for that, I will dig it back out of the junk pile and have another look at it, see what happens, cheers

@wilky Let us know what the outcome is.

Posted by: @wilky

will what I have done is cut all but 3 12v side wires out, same with the ground and same with the 5v side plus used the resistor. On the 12v side I have a single plug to power up an lcd screen controller board and on the 5v side I connected a usb socket so I could run usb fans etc. I have measured the voltage from the cables and from the fittings and still get the same result.

[I am somewhat confused... I was certain I answered this thread earlier, but I can't see my reply anywhere. I wonder if I wrote it up and forgot to actually send it.]

It seems very likely that you've snipped the sense lines. Some of the lines from the ATX to the plug are for the power supply to get feedback to correct the output voltage. If you cut all of the lines, they're probably floating. When you use an ATX supply to make a power supply, you need to be sure to preserve these sense lines back to the supply.

There's even a possibility that you've inadvertently tried to use a sense line as a power line.

@jker That makes a lot of sense, there was a yellow with black stripe on it, I did wonder what it was and now I think I know, I have since binned the psu and will get another one, I was given a pc to get the power supply out of but I got the pc running a treat. Will hunt one down and try again making sure I work out the sense wires first, that makes sense 😀 thanks for the feedback. cheers Wilky