bench supply

[Shawn Wilson]

I converted computer power supply to bench supply a few years ago.  It died recently, and I'm making a new one.  I basically cut the wires and wire nutted them together by color.  I took one of each 3.3v, ground, 5v, -5v, 12v, -12v to banana jacks and wire nutted the green to ground.  Now when I turn it on, I get power for a second, then nothing. Power supply fan doesn't come on at all. I tried it with a load (12v marine blower).  Same thing.  I know it was working before I started my mods.  Any suggestions?

[Real O'Neil]

I'm guessing you already checked to make sure what it's plugged into is grounded properly?

( I mention this only because once upon a time I had a borked outlet and found out when a grounded connection wasn't )

On Tue, Apr 19, 2016 at 12:41 PM, Shawn Wilson <sh...@glassgiant.com> wrote:

I converted computer power supply to bench supply a few years ago.  It died recently, and I'm making a new one.  I basically cut the wires and wire nutted them together by color.  I took one of each 3.3v, ground, 5v, -5v, 12v, -12v to banana jacks and wire nutted the green to ground.  Now when I turn it on, I get power for a second, then nothing. Power supply fan doesn't come on at all. I tried it with a load (12v marine blower).  Same thing.  I know it was working before I started my mods.  Any suggestions?

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[Chris McDonald]

Check that the v+ lines you connected are all from the same trace on the PSU. A quick test is just to disconnect them all. Other than that you may have to disassemble the supply and look at the bottom of the PCB. 

Most modern PSU's have a number of separate output stages for for 12v and sometimes 5v. The label will indicate if so. It will have something like 12V1 and 12V2 with different or the same current ratings. Connecting them together has undefined behavior. They might fight each other and cause the overload situation your getting. 

[Evan d'Entremont]

You'll want to throw resistors across either the 5v or the 12v depending on the PSU; makes it more stable. 

On Tue, Apr 19, 2016, 12:41 PM Shawn Wilson <sh...@glassgiant.com> wrote:

I converted computer power supply to bench supply a few years ago.  It died recently, and I'm making a new one.  I basically cut the wires and wire nutted them together by color.  I took one of each 3.3v, ground, 5v, -5v, 12v, -12v to banana jacks and wire nutted the green to ground.  Now when I turn it on, I get power for a second, then nothing. Power supply fan doesn't come on at all. I tried it with a load (12v marine blower).  Same thing.  I know it was working before I started my mods.  Any suggestions?

[Shawn Wilson]

Thanks, I'll try all these, except the label thing.  The label was on the side I'm using for my jacks; I sanded it off without having the presence of mind to take a pic first. Duh.

[Real O'Neil]

Lemme know how it works out, since I've been wanting to do this for a while now since my usual PS got busted. In case I run into the same :)

[Shawn Wilson]

No joy.  I cut all the bundles so they didn't touch (couldn't see exactly where the wires met the traces on back).  Double checked the 'power good' was grounded.  Put a 10w, 10ohm resistor on the 12v, 3v, 5v. I do get 5v on the purple standby power but no power on anything else.  PSU fan doesn't spin.

Real, if I end up doing this again, I'll make a little bigger box that I can stick a PSU inside and plug in the 20 pin connector.  The box will have the banana ports and mains power switch.  So the next time it dies, I can just unplug it and plug a new one in.  The size savings  isn't worth the extra effort, IMO.

[Real O'Neil]

Not a terrible idea. Definitely a fan of swappable interchangeability :)

[Adam Cox]

I picked up one of these a while back and just have to solder it up. 

https://www.sparkfun.com/products/12867