11.4V on 12V rail with YoungYear ATX PSIV-400-2

[retiredcaps]

1) I bought an used Celeron 2.8GHz system recently and it came with this YoungYear ATX PSIV-400-2 power supply.

2) On the BIOS screen, the 12V rail shows 11.4V. I read that the 12V rail can be +/- 5% and 11.4 is just on the low end. Should I be worried? The computer has 1 floppy, CD-RW, two 20GB hard drives, and 256MB DRAM.

I will only be using this computer with Internet use (web browsing, email, youtube, etc). No critical data will be saved on the hard drives. When not used it will be turned off via power bar.

3) I took apart the power supply and noted two TNR 470uF 10V caps bulging. With all the glue/tight fit, the only 16V cap that I can see is the biggest one in the top right hand corner (Fuhiyyu 2200uF 16V). There may be others on the 12V rail, but until I take more things apart, I don't know for sure.

[TheLaw]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

The PSU is pretty garbage but BIOS/software voltage monitoring is highly unreliable.

Even if 11.4V is a true measurement, it is still technically in spec, albeit the minimum voltage allowed to still comply with ATX specification.

Don't worry about it. BIOS voltage readings aren't reliable. I don't even know why they bother putting that feature in.

[retiredcaps]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

The PSU is pretty garbage but BIOS/software voltage monitoring is highly unreliable.

I didn't expect much of a PSU for the price I paid.

I shorted out power and ground and I measured 10.65V DC on the 12V rail with my Fluke 75 multimeter. That is with no load whatsoever. Same reading of -10.65V on the -12V rail.

[retiredcaps]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

Hmm, out of curiousity, I just happened to have another power supply sitting around and I shorted out power and ground and I measured 12.07V DC on the 12V rail (again with no load).

Can I conclude then that the YoungYear reading of 10.65V DC indicates something wrong? Or is the test invalid without a load?

[370forlife]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

Hook up an old hard drive and or fan to it for a light load and see what happens. Usually 10.XX volts is low enough to trigger the UVP protection, and I doubt the computer would start with that low of voltage.

[momaka]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

One of the bulged caps seems to be on 5vsb and that's not good for your chipset. The PCB near the 5vsb circuit is also starting to burn up - that means impending failure on 5vsb unless the critical cap in that circuit is replaced.

I think it's time to retire this PSU and maybe use it for parts only (unless of course you plan to recap it or just use as a bench power supply for powering non-important things).

[Trinite]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

Hook up an old hard drive and or fan to it for a light load and see what happens.

Yep. A lot of PSUs tend to be whacky on voltages unless you load down the 5V rail somewhat.

[retiredcaps]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

Hook up an old hard drive

I hooked up a CD-RW and 20GB hard disk and got 11.51V DC on the 12V rail with my Fluke 75.

Thanks for all the suggestions. I learned quite a bit today.

[retiredcaps]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

I think it's time to retire this PSU and maybe use it for parts only (unless of course you plan to recap it or just use as a bench power supply for powering non-important things).

My plan is to recap and use it for Internet usage machine with no critical data sitting on the hard disks.

I may take that Celeron 2.8Ghz and put it into my "main" computer which is a 2.53Ghz. Yes, I live in the previous generation CPU world! But it serves my needs just fine.

[Th3_uN1Qu3]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

I'd upgrade to a low-end C2D if i were you, this is coming from someone who had been pushing a P4 for many years. A world of difference both in speed and power efficiency.

[ratdude747]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

i would toss that psu into the scrap parts bin.

youngyear=cheap crap. i even heard they once were so cheap they only used 2 screws to hold in the fan.

plus, anything with bad caps i do not recommend using without a recap. doesn't matter how little load is on it, if it's broken, it's broken.

[momaka]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

My plan is to recap and use it for Internet usage machine with no critical data sitting on the hard disks.

In that case, make sure to change all of the caps on the secondary and maybe even upgrade them if they need to be. For example, if the 3.3v or 5v rails have anything less than 2x 2200uF caps each, then change the caps so that they do. The 12v rail is also very important - in fact the most important here, since you'll be powering a P4. Get at least 1x 3300uF in there.
And don't forget the critical caps near 5vsb (usually 10, 22, or 47uF) as well as the caps on 5vsb itself.
Last but not least, check the capacity of the 12v rectifier. For a P4, you'll want at least 16A.

Yes, I live in the previous generation CPU world! But it serves my needs just fine.

Same here. Actually, I still have (and use) Pentium III's as well. They work rather fine for light web surfing and downloading things. When I feel like watching YouTube (or surfing badcaps.net), though, I sit on my family's computer (2.8GHz P4). It's a lot more more quiet.
My gripe with the older P3/AMD K7 computers is that they have those noisy 5-6 CM fans that always run at full speed and sound like jet engines. When I listen to music, that's not a problem and it doesn't bother me, but when I need to write a lab report, the sound begins to drive me nuts. It doesn't help that the hard drives in those machines are old as well - their bearings are almost as loud as the fans.

[momaka]

Re: 11.4V on 12V rail with YoungYear ATX PSIV-400-2

Upon a second look at the PSU, it seems that there's more work to be done besides the recap.

1) Remove the load resistors between the capacitors on the secondary side. I can see two (one is next to the bulged cap near the coil, the other is slightly above that in the picture). There may be 3 or more, actually - usually one for each rail. The one next to the other bulged cap is likely between 5vsb and ground - please check. If it is, remove it. The reasons you want these gone is so that they don't cook your new caps.

2) The primary side is missing a safety X cap (between fuse and filter choke). Find one and add it in there.

3) The 3.3v rail seems to be derived from the 5v rail via MOSFET - in this case, if there is no space to put 2x 2200uF on the 3.3v rail, 1x 2200uF or 2700uF will likely do fine as well.

4) Also change the 2 small caps on the primary side between main transformer and primary heatsink. Those are responsible for driving the primary transistors and may impact the efficiency of the PSU.

Overall, that's lots of work. But I'm with ratdude here - don't use it if you don't recap it.