Faulty -5v lines?

[boshuda]

I recently ordered a replacement Shuttle PC40 P/S when the computer was giving me odd errors. I checked the voltage on the unit with a Power Judge tester and a Coolmax PC/SPS TesterI. Both showed error on the -5v setting on the 20pin ATX. The Power Judge also has an over voltage LED, showing the P/S was over voltage.

I ordered a replacement because I'm not ready to attempt recapping. The replacement supply showed the same error. I thought maybe it was my testing units, but they work fine on other P/Ss. A Dell P/S (hp-l1116f3p) which is also a slim unit like the shuttles (although not quite as small) had the same result on those tester units. This P/S's fan had failed over night, and some of the capacitors inside appeared bowed (I didn't open it, it's a customer's and they just had it replaced yesterday). I've also noticed this -5v problem on other Shuttle P/S's, and some other systems - like HP and Compaq.

I'm posting because I would like help determining what the problem is, how I can fix it, etc. Basically any advice anyone can provide would be great. I can't post pictures today (no camera), but I should be able to tomorrow.

[Rainbow]

Re: Faulty -5v lines?

Some PSUs don't have -5V line at all - check the ATX connector if it's missing.

[boshuda]

Re: Faulty -5v lines?

So simple - yet that was the issue. Looks like my ignorant self will end up eating the cost of a replacement unit - but at least I've learned my lesson.

Thanks so much for the (amazingly) quick response.

[Per Hansson]

Re: Faulty -5v lines?

Yes, it was removed from the ATX spec in one of the more recent revisions, 2.03 maybe?

-12v should still be present...

On one mobo I actually heard it could cause problems, because the built in sound was designed to require -5v, what a bummer :P

[japlytic]

Re: Faulty -5v lines?

The -5V rail is only used by the ISA bus, and is very rarely used (devices such as data separators in very old floppy controllers). Some boards with an ISA bus have a -5V regulator for this bus.

[Galvanized]

Re: Faulty -5v lines?

I have read that some older sound cards used the -5.
I think it was a recent MSI board that went unstable w/o the -5.

The -12 is soon to go.

[Rainbow]

Re: Faulty -5v lines?

-12V is needed for serial ports and is also present on PCI.

[Brian C]

Re: Faulty -5v lines?

Since u ordered the replacement p/s. It shouldn't have caused any problem. perhaps mobo spoilt ?

[Brian C]

Re: Faulty -5v lines?

For ur info. PC40 p/s doesn't have -5v supply line. That is why it shows error on the tester.

[gonzo0815]

Re: Faulty -5v lines?

Some recent ASUS board need the -5v too for onboard sound. Not all tech`s have read the new ATX spec or to be more precise Intel`s suggestion of this carefully. Following that, any 24pin PSu should not have the -5v line, but hapily most PSU vendors have not followed this spec. But at least some FSP and many Enermax units have the -5v line removed.

[boshuda]

Re: Faulty -5v lines?

Thanks for all the replies, I was actually going to ask about the ATX spec thing, since I figured if the -5v was in the spec then different components might need it. Now I know better. So nice to post to a board with people smarter than me And every day you learn something is a good day. Today and yesterday I learned many things, perhaps chief among them to read the stupid specs.

And the problem was that the CMOS battery was low. It was still keeping time, despite being unplugged for several days, but the default values were preventing it from booting and changes wouldn't save consistently.

[Galvanized]

Re: Faulty -5v lines?

The -5 will be a white wire in the #14 position.
You can find all kinds of tid-bits at formfactors.org. The site is well worth looking over.