Antec SP-400 on knees and crying pulling a P4...

[eccerr0r]

What do people think...

I have an Antec SP400 - the same one that I repaired, had to replace 5VSB caps and the switcher IC. It was working fine with 4 HDDs on a 3GHz P4 (Pres-Hott), but when I hooked up three more HDDs, it wouldn't turn on! Remove some HDDs and it works again. It might be the spin up surge of the HDDs but it's pretty rough.

Maybe I have more bad caps? This machine also would not power up with an Antec SP300 when it just had 4 HDDs, hence I had to put in the the SP400. Maybe the SP300 also needs new caps too.

I dropped in that BBQ'ed 750W PSU I just repaired and it started up just fine.

[stj]

Re: Antec SP-400 on knees and crying pulling a P4...

could be caps,
could also be the fact that ide/sata drives spin-up when you connect the power.
this is shit, because you get a big surge.

if it was scsi the drives would spin-up in sequence so as not to shut your psu down!!

[eccerr0r]

Re: Antec SP-400 on knees and crying pulling a P4...

Yeah, SCSI drives have delayed spin easily controllable via jumper. SATA and PATA drives usually do not.

It looks like a typical drive draws 2A on the 12V rail on first startup. So 7 hard drives trying to spin up is 14A =~ 170W. Then average out the 5V supply at .5A per disk = ~ 18W.

Round that off to 200W. Wow, that indeed is quite a bit of pull for 7 disks.

The pres-hott I've seen shoot up to 100W during boot (once I was running a gpu and a pres-hott and the pair drew 180W+ during boot...)

-> A 400W PSU should be able to easily start these disks, it seems, as long as there's no GPU?

[Behemot]

Re: Antec SP-400 on knees and crying pulling a P4...

I think the start-up surge is even higher than what the disks are labeled, it's like with incandescent light bulbs…

[eccerr0r]

Re: Antec SP-400 on knees and crying pulling a P4...

The labels tend to write less than an amp on +12 (I just noticed two of my WDs are only 600mA). I saw a website that measured the peak to be around 2 amps when the disks start spinning so that was the value I used. Of course this is drive specific, and suspecting disks with more platters to be worse.

[momaka]

Re: Antec SP-400 on knees and crying pulling a P4...

The labels tend to write less than an amp on +12 (I just noticed two of my WDs are only 600mA). I saw a website that measured the peak to be around 2 amps when the disks start spinning so that was the value I used. Of course this is drive specific, and suspecting disks with more platters to be worse.

Yup, normal to see lower Amp ratings on HDDs than what they actually use at startup. 2 Amps is a good assumption, so your calculations above should be pretty close.

With that said, you have 100 Watts for the CPU + 180 Watts for the HDDs + 10-20 Watts for the fans and other misc stuff + xx watts for the GPU... so you probably need over 300 Watts on the 12V rail. Is the SP-400 capable of that? Is it capable of that without much load on the other rails? All these can cause the PSU not to work. Add bad caps on top of that, and that could well be why the PSU is not wanting to work.

[eccerr0r]

Re: Antec SP-400 on knees and crying pulling a P4...

The SP400's rating:

+5: 28A
+3.3: 30A
+5 and +3.3: 130W max draw. Likely mag amped.

+5VSB: 2A

+12V1: 14A => 168W max
+12V2: 15A => 180W max

-12V: 0.3A
Total: 400W max

This technically should be enough (the rails seem to actually be tied together), very possible it's just capacitors. The machine uses the onboard graphics so at least it doesn't need to power a discrete GPU along with the mess.

Looking at the Antec SL300S, it's very clear why it can't supply 7 HDDs, as it seems to be +5/+3.3 heavy and doesn't pay much attention to the +12 rail as it only has one 15A output. Come to think of it, I think this SL300S is very poorly matched for the P4 as the +12 rail is very underpowered if it needs to power both the VRM and the HDDs. No wonder why it has trouble even powering a few HDDs with the P4.

[momaka]

Re: Antec SP-400 on knees and crying pulling a P4...

+12V1: 14A => 168W max
+12V2: 15A => 180W max

That doesn't tell you much, though.

Most PSUs with more than one 12V rail will give a max combined power rating too. Without one, you can only assume what it could be. From what I've see on other PSUs before, your PSU is probably good for no more than 20-24 Amps total combined on the 12V rail.... or about 240-288 Watts. And that's probably if you have a somewhat bigger load on the 5V rail too (that's where motherboards with power-hungry Northbridges are useful, as those are typically powered by the 5V rail).

Come to think of it, I think this SL300S is very poorly matched for the P4 as the +12 rail is very underpowered if it needs to power both the VRM and the HDDs. No wonder why it has trouble even powering a few HDDs with the P4.

With 2 HDDs or less, it would probably be okay. The problem is that Pentium 4 also has a high power draw at boot.

That Antec SL300S may also be a bit more sensitive than other PSUs. I was using a 250 Watt HiPro to power an Athlon 64 3500+ (67W TDP) and a Radeon HD3870 video card (~90W TDP) with two heavy multi-platter HDDs, and never had a problem playing games and maxing out the video card. Sure the PSU got warn then, but it managed. 12V rail never dipped below 11.85V.