Silverstone ST85ZF 12v1 & 12v2 question...

[Aalelan]

Ok, I read Jonny's review and I'm quite excited about this PS, I have a Fortron (FSP550-60PLN), and keep overloading my 12v2 rail :( I have not been able to find the answer to a question of mine.. Or if just keep missing it :D

From His review:

"But because the ST85ZF only has an 8-pin EPS+12V connector, an adapter is needed to bring this down to a four pin ATX+12V motherboard."

"# 12V1: CPU-1. Typically powered through the 4-pin connector of a power supply. On the ST75ZF, power for CPU-1 is provided by the first two 12V wires on the 8-pin EPS+12V connector.
# 12V2: CPU-2. Typically, dual CPU motherboards that would require each CPU have its own 12V rail would get it's power from the second two 12V wires on the 8-pin connector. Silverstone also puts the SATA connectors on this rail as well as PCI-e connector #3."

and this image http://www.jonnyguru.com/PSU/ST85ZF/IMG_1105.jpg

Given that info, here is my question.. If you need the 4-pin connector for your CPU power and you use the 8>4 pin converter.. Does it not in fact "Join" those two rails?? Splitting the load between 12v1 and 12v2??

If, that is the case could this happen? More load on 12v2 from other components than there is on 12v1, will there be a "balancing flow" of current through that adapter between the two rails?

Forgive me if that is a totally absurd question, I have only basic electronic knowledge, sometimes just enough to make me over think things..

Thanks in advance!!

[Oklahoma Wolf]

If the adaptor they use with the 85ZF is the same as the one with my 56ZF, the 4 pin adaptor only gets power from half of the EPS connector. In that case, the two rails would not be combined.

How are you managing to overload 12v2 of that FSP? I would think 12v1 would be more of an issue, given that 12v2 is for the CPU(s) only.

[Aalelan]

Thanks for the info Oklahoma Wolf, The image was what really confused me, looks like they took they took the four common from the 8pin and ran them down to two on the 4 pin and likewise on the +12v.

"overload" was a missuse of words on my part.. I should have said (and this all revolved around my though that the "rails/lines" were merged.. That the 12v2 would become more loaded that 12v1 since it has the SATA conectors on it too. Granted it would not be a ton of load, I think the 4 drives I'm putting on will only amount to 2-2.5A.

Like I said sometimes I just make things harder than they should be.. You should see the legal pad where I drew this all out and did my math :D I just want to make sure I'll be ready for a Kentsfiled overclocked on my water setup with a G80 down the line or maybe 2 in SLI if I can find a way to get a nice large monitor ;) I thought My Fortron 550 would last me a while, but I seem to be overloading it, its lead a hard life over the last two years too. It could just be getting weaker.

[Oklahoma Wolf]

I was looking at the pics again and it does appear the adaptor sums the rails.

That particular FSP unit is one of their better independantly regulated server units - it should still be ok, though it's a two PCB design that uses the case for cooling. Could be it's been getting hot enough to cook the capacitors, though FSP used mostly Teapo in these models.

The 85ZF is definitely a worthy and better replacement though ;)

[Aalelan]

OK, so I'm not crazy on that adapter :) Given that would it cause a balancing effect on those two rails?

Yeah, the FPS I have blows heat like a hair dryer out the back.. Maybe I can swap out the fan for a higher CFM, I wont mind the extra noise if it can make me wait a little longer on replacing it.. I've run an old Antec 350 +12 feed into my case to power my 7900GTO for the time being, it seeems to have solved my problem for now :D

[jonnyGURU]

The ST85ZF adapter splits the load of the 4-pin across the two rails (12V1 and 12V2.)

[Slartibartfast]

You could get some blue-tack (sp?) and use it to mush a fan on to the back of the FSP and force some more air through.

[Aalelan]

Thanks for the info!! I think I have the answer I'm looking for now. sometimes I can be a little :crazy: I was seeing it (the adapter) as being able to "bond" and balance the two rails as a whole, given that they were connected.. I guess that is not the case. Off to do some reading so I can understand why that is.

Thanks again! BTW Your reviews are awesome Jonny!!

[jonnyGURU]

Thanks for the info!! I think I have the answer I'm looking for now. sometimes I can be a little :crazy: I was seeing it (the adapter) as being able to "bond" and balance the two rails as a whole, given that they were connected.. I guess that is not the case. Off to do some reading so I can understand why that is.

Why would that not be the case?

Sorry I didn't get a chance to read all of the back and forth between you and OKW, but if you have a 10A load on a four pin, and that four pin is split up across two rails on an 8-pin, you're essentially splitting that 10A load in half for each of the two rails.

The only fluctuation from 5A per rail would be the mV difference created by resistance in the connector, length of wire, etc.

[Aalelan]

Ok, I'm just not conveying myself properly in the written word :) Let me see if I can draw this..

12v1............12v2
....V..............V..V
....V..............V..---SATA Devices--5A--
....>>> 8>4 <<<
............V
.....---CPU-10A---


Well that came out better than what I thought it would :D

How many amps are on 12v1 and 12v2 in this setup, given that the "8>4" thing is the adapter? Is it 5A on 12v1 and 10 on 12v2 OR is it 7.5 on both, since they are technically bridged/bonded at that adapter point..


Well when I posted it it striped out all my spaces in my drawing, trying to fix it.. Ok I ignore all the ....'s in the drawing only way I could get it to format right..

[Oklahoma Wolf]

7.5A on both, give or take a few mA.

[jonnyGURU]

It would be 5A per rail. If you have a 10A load, and you split that load across two rails, then you split that load in half. 5A per rail.

Since it looks like you have 5A worth of SATA devices also hooked up to 12V2, then you would have a 10A load on 12V2.

So, in summary, 10A load split between 12V1 and 12V2 and a 5A load on 12V2 equals a 5A load on 12V1 and 10A load on 12V2.

[jonnyGURU]

7.5A on both, give or take a few mA.

The SATA drives aren't going through the adapter and isn't loading +12V1, so it's 5A load would not be part of the split. It's its own load.

[Oklahoma Wolf]

Yeah - I was responding to the diagram even though I couldn't see how the SATA drives were on 12v2.

[Aalelan]

Well, Found my problem... Decided to pop the hood on my FPS. and found that I was only really using one of the two rails.. the 4 pin that I thought was on rail 12v1 going to the CPU was in fact on rail 12v2.. The only thing that was on 12v1 was the 8 pin connector that I was not using :mad: SO, for two years I have only been using half of this PS...

well 10min later, after some snips, pulls, solder and a little bit of heat shrink.. my CPU power is all on 12v1 and the rest (including my video) is on 12v2.. Also found the rail voltage pots when I was in there poking around and tweaked them just a touch.. Over all system is ruing much better now... I think I'm just bound by this proc or MB now... temps at full load are only at 38C, and I have lost all the bounce in my +12 reading on my asus voltage monitor too!!

Sorry for all the crazy questions and thanks for all the help!!

Aaron

[jonnyGURU]

Wow!

So FSP had the 8-pin on 12V2 but the 4-pin on 12V1?

That's messed up. :lol:

[Oklahoma Wolf]

I was only really using one of the two rails

That could explain things ;)