Announcement

**linuxguru** · 11-13-2006, 07:08 AM

Re: minimum load on 3.3v & 5V rails ?

Exactly how are you going to sequence the power up of all the rails? Only one of the ATX 20-pin connectors can be connected, so you'll have to short the PSON signal on the other one to ground; this will leave that PSU always on along with all the drives and the AGP card connected to it. It's a sure recipe for busting the AGP card and the mobo.

**hkivan** · 11-13-2006, 07:55 AM

Re: minimum load on 3.3v & 5V rails ?

nope, I connected the pin 14 & pin 15 to the respective pins on the primary PSU.
They can start & stop together .

**yanz** · 11-13-2006, 09:11 PM

Re: minimum load on 3.3v & 5V rails ?

i would better having many big resistor of fairly bigger ohm like 15-68 ohms so they aren't running too hot for short period of testing like 15-20mnt. if the psu will be on for long time than you need to make a box of dummy resistor with its own fan(s) cooling. or just run wires and glued the resistors to computer case.

btw total load of 4-10W per rail is enough, i think. cmiiw. i also would like to 'enhance' the 12v output filter section on that v1.3 old psu. usually they only have little capacitance, and i would remove any small dummy resistors on the o/p filter area, or if i worry it will have bad effect, i'll replace it with external dummy ressistor that glued to psu casing.

**starfury1** · 11-14-2006, 06:11 AM

Re: minimum load on 3.3v & 5V rails ?

Hi all

Seems there is a lot of pages on dual psu setup
(weather its a good idea or not, I dont know)

this for one

http://www.burningissues.net/how_to/power/psu.htm

Running HDD's fans off one may be one thing

I am no expert on this but do agree with linuxguru connecting 2 different psu +ve to a possibly common supply rail AGP MB may be a recipe for trouble.
(not sure how the extra supply works with AGP pcb's)

The voltage would not be exactly the same (may only be a few hundred millivolts) but there would have to be some interaction between the two PSU's (Voltage/current sources)

Also timing as the rails come up would be some what different even if you trigger the same time

If you must... and if it was me, id be putting AGP CPU MB on one supply only.

There are others here that know a lot more then me here so i'll leave it to them.

Best option a BIG psu I suppose, anyway Goodluck with it

**hkivan** · 11-18-2006, 11:38 AM

Re: minimum load on 3.3v & 5V rails ?

Thank you for all of your info.

Right now, my system is running with Dual PSU setup. The slave PSU is behind the 12cm front fan and I glued it with a hot glue gun. It work fine if the AGP molex is connected from master or slave psu but evetually,I connected to the master PSU as advised.

I desoldered all wires from the ATX 20-pin of the slave PSU except pin14 & 15.Well, is there any problem for not connect the PG wire to ground ?

FSP and Thermaltake has their VGA PSUs which are dedicated to power graphic card only. I am thinking if we can make a PSU to work in that way. Of course, one "Big" PSU is always better but it will be more expensive.

The dummy resistors are connected as follows :

5V --- ----10w5RJ---5w1RJ--------------
3.3v ------10w5RJ-----------------------
3.3v ------5w1RJ---5w1RJ ---5w1RJ -----

~ 4.2W on 5V rail
~ 5.8W on 3.3v rail

**starfury1** · 11-22-2006, 09:22 AM

Re: minimum load on 3.3v & 5V rails ?

Hi HKivan, All

Been meaning to get back to this post

OK bear in mind I will stand to be corrected on any of the following;
(guru's here

)

The PG your are refering to (I hope) is output from psu to tell MB not to fire up just yet! (to put it basically)
Till once supply rails have fully stabilized.

pg explained

So on secondary supply you dont need to connect it anywhere.

I haven't had a chance to check on this AGP supply thing
(seems its being done thought)

I don't know what would be the optimal values of current to load the unused rails with so guess yanz's the man for that answer (above)
not too much not too little

Giving it somthing to bite on is a good idea thought as it will help stabilized it
(older supplies colud die from no load, at best shutdown)

since its working, Iam guessing the negative/ground whatever is being tied together via the psu cases.

I know there are ways to actually force sharing of supply outputs but this would result in voltage drops I expect not to mention extra parts and a rewiring nightmare.

Seems many people are doing what you are trying to do and there seems to be information out there on it

This idea of paralleling psu's does raise an interesting point thought...what about all the new ones comming out with dual (or more) supply rails

If I remember the tibits from my liberty...you can only use certain rails for certain things.....

Anyway my train of thought is stating to drift a bit off topic here

Cheers

**gonzo0815** · 11-22-2006, 04:06 PM

Re: minimum load on 3.3v & 5V rails ?

Well, the problem of dual PSU load is the current sharing. If one PSu have little higher voltage, it will overtake the whole load. The best thing would be a controler, wich regulates both supplies to have equal sharing (those are availiable ). But if you power a GFX card and some HDD`s (just to get the minimla load on 5v) with one psu, and the board & cpu with the other should work, as those Buck regulator have diodes on it. The question left is if potential differences between both PSU circuits can occure. If there are some, there could be a delta voltage between the signal interfaces e.g. HDD cable, if board is powered with an different psu than HDD. To avoid this, it would be good to conect the ground wires of both PSu`s. Porbably, this would be done anyway, as all the ground layers are conected. The other problem are the input filter, wich can conduct some mA from the mains. But if both psu`s are mounted in a metal case, this should be no concern.

**starfury1** · 11-23-2006, 12:12 AM

Re: minimum load on 3.3v & 5V rails ?

Thanks gonzo0815

For putting that in a much more clearer context

The question left is if potential differences between both PSU circuits can occure. If there are some, there could be a delta voltage between the signal interfaces e.g. HDD cable, if board is powered with an different psu than HDD. To avoid this, it would be good to connect the ground wires of both PSu`s

Signal interfaces,
that was my other concern which I hadn't really raised yet

As to the AGP extra power connector and I have yet to confirm any of this

The reason is to provide extra power (current really I guess) that can't be provided by the normal AGP slot connector.

The psu's that have this connector I am guessing take it from the same internal supply source, just via a more current capable connector.

Yet to confirm this thought.

Seems the way people are using a dual PSU setup is powering HDD CDrom case fans etc off the secondary and using the primary for MB and anything hanging off it AGP CPU fan

Oh yeah can you please post some photos of the setup,
would be nice to see what we are talking about

Cheers

**hkivan** · 11-23-2006, 11:27 AM

Re: minimum load on 3.3v & 5V rails ?

starfury1 , gonoz0815

Thanks for your info.

My setup is quite ugly. Many wires messed up inside the case. The GFX card is recaped ugly too. The slave PSU is inserted and glued into the 3.5" HD position right behind the front 12CM fan.

After removal of the IHS, my sempron 2800+ runs at 2.4Ghz with 1.62V , 50C on loading. With 100Mhz ram divider , it can runs at 2.7Ghz. Right now, it can run upto 2.65 by using ClockGen while 300Mhz HTT is max. out in BIOS.

My next move is to volt-mod Vdimm of mobo & 3.3V rail of the master PSU.
But, before that, I wish to recap the master PSU as I find some "SC" on the output side. By the way, can you tell me any the "SC" brand cap which I can't find any info on this site?

**hkivan** · 11-24-2006, 08:04 AM

Re: minimum load on 3.3v & 5V rails ?

The attached image shows what the "SC" cap I metioned eariler.
I found from some reviews that they are inside some low end PSUs.
I'm thinking if "SC" is crap. They are populated on the secondary side
on my PSU. I will probobaly recap them with same uF for safe.

My main PSU is a GTR AP450X. The brand "GTR" is by no mean related to any sport cars. In fact, GTR in hongkong has very limited products on the high end. It's PSUs are mainly of entry level to mainstream.

I gonna modify the 3.3v sense wire to have 3.4 to 3.5V. For that I don't need to do anything on mobo in order to rise a bit the Vdimm.

Attached Files

**starfury1** · 11-25-2006, 08:32 AM

Re: minimum load on 3.3v & 5V rails ?

Hi Hkivan, all

well I cant help you with the caps (as to quality etc) but guess since you are going to give this thing a flogging and it sounds like you might be in the right place to source high quality caps at a reasonable price.
(and you know how to recap) I would recap it.

Found a review on your GTR AP450X psu.

Here

Also off one of his link pages found this!

sharing the load psu outputs

how well or the pros and cons, don't know I haven't really look at it yet

also this might be worth a read

link from review page

anyway just my thoughts on it (and a few links)

cheers

**starfury1** · 11-25-2006, 08:50 AM

Re: minimum load on 3.3v & 5V rails ?

DOH! its the 480 not 450... same mob, wrong supply by the looks of it

Humm GTR website only has 430 480...oh well probably close

**hkivan** · 11-25-2006, 10:08 AM

Re: minimum load on 3.3v & 5V rails ?

Thanks again starfury1

My model is GTR AP450X which is a difference series to GX .
It comes with 14cm fan without the cable management feature but,
I will make the unoccupied molex cables modular later !

Your links info are very informative too. For the "SC" cap, I'm not in hurry to recap them. I wish to know more about the "SC" cap... the name of the brand , specifiaction ...etc

I do find some sources of YXA ,YXG , MBZ ....and I have some KZE , KZG & sanyo WG desoldered from mobos.

3.3v 3300uF MBZ cost HKD$6 . Is it reasonable ?

**gonzo0815** · 11-26-2006, 05:22 AM

Re: minimum load on 3.3v & 5V rails ?

I duno, wich brand those SC caps are, but i belive they are somhow liked to Fuyihu crap. I have had several real BS PSu`s wich have those ugly saturn symboled caps too.
Alle caps on them are from Fuhiyu too. I am not shure, but IMHO there are some post abouth those Saturn symbol caps here. But may be a little hard to dig them out. Any way, AFAIR they are considered as crap. But ok, primary side caps aren`t the number one probleme, thus you can wait until you can source better ones.

**starfury1** · 11-26-2006, 10:20 PM

Re: minimum load on 3.3v & 5V rails ?

I just "copy paste" you model into google silly me didn't pay much attention to the number... like I said DOH!

I vaguely remember trying to find info on those caps a 2 years (there abouts) back didn't have much luck then or now.
even tried doing a photo search on google to see if I could get a lead
they are fairly common so guess someone must know who makes the things.
Only came up with the teapo SC green gold low esr.

You said if I remember correctly, they are also on the secondary side same brand "SC"
If it was me I'd change them to good quality ones.....gonzo0815 comment on them as being towards if not crap would make sense since they are fairly common in cheaper supplies...so yeah since they are going to be the most expensive to replace...as he said...

As to price don't know... nothing cheap in OZ now if you want quality caps
(well at retail I suppose)
there is a forum member from your local will see if I can find him and pm him.

**Big Pope** · 11-26-2006, 11:48 PM

Re: minimum load on 3.3v & 5V rails ?

Originally posted by hkivan

3.3v 3300uF MBZ cost HKD$6 . Is it reasonable ?

Yes, reasonable if it is a shop. A shop need some costs every day.

If you want to try my Samxon for quality view, just let me know.

Announcement

minimum load on 3.3v & 5V rails ?

minimum load on 3.3v & 5V rails ?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment