Guide: Power Supply Sense Wire Modding

[DarkManX_BG]

Originally posted by Hell-Fire
Definitely use a DMM when adjusting the VRs...never trust the bios for an accurate reading on any voltage.

I second that... a while ago, I trusted BIOS after doing a vdimm mod and thought that I'm running safe 3.02V... it turned out my memory actually got 3.11V, which scared me at that time (now I run 3.2V 24/7, times have changed )

[NoX]

Originally posted by Hell-Fire
Definitely use a DMM when adjusting the VRs...never trust the bios for an accurate reading on any voltage.

Is it possible to measure the core and the +12V rail voltages with a DMM when the CPU is running under load?

Thanks.

[Hell-Fire]

Originally posted by NoX
Is it possible to measure the core and the +12V rail voltages with a DMM when the CPU is running under load?

Thanks.

Yes sir. Check the 12v rail by sticking the red probe into a molex connector (plugs into hard drives, fans, etc) slot that has a yellow wire in it, and the black probe into a slot with a black wire in it.

To check the core, I am supposing you mean Vcore (CPU), then you need to check any Chokes and FETs that are around the cpu socket.

Be careful not to cause a short circuit.

[NoX]

Thanks Hell-Fire for the quick reply. I have just a few more questions. Please be patient with me, I am a mech engineer messing around with electrical devices.
I checked the +12v rail an it fluctuates between 11.9 and 12.2 volts. The vcore droips by .07-.08v under load. Now what would be the benefit of modding the PSU and increasing the 12v? Will this stabilize the vcore?

[STEvil]

may help some.. but if your rails are fluctuating it may be better to get a better PSU.

[Hell-Fire]

Agree with STEvil, and hav another option to consider.

Yes, sometimes modding the rail will help to steady her out a bit.

You need to check to see if the exhaust air is warm or not. If so, you should consider changing out the stock fans for something with higher CFM. The higher the temps get inside a psu, the more the output suffers and stability.

[DarkManX_BG]

Did the mod a couple of days ago, works like a charm. 3.6V is safe for 24/7 use, isn't it?

I can confirm that the mod works without the fixed resistor on an Enermax 460W btw

Oh yeah, I did the noobish mistake to solder to the wrong ground wire - I used the one that goes to the mobo instead of the one that goes back to the PSU how stupid of me. Still works though, as we all know - all ground wires are connected... multiple times :P

[NoX]

Indeed my Allied 500W PS is definitely warm during the day and I noticed that at night, when it cools down, I can push the OC further. Better CFMs may help but probably not that much because the room air temp rises over 30C (California’s summer hell). However, I'll get some better fans, it will help anyway. I am tempted to get the Fortron 530W but I am afraid that it will end up with even worst performance because of its case made of steel (the Allied is made of aluminum). Hmmm, maybe I should figure out a way to watercool the PSU. In fact, I think that what I really need is a vdroop mod for the mobo. I did a lot of research but I couldn't find anything about it. I only hope that Hell-Fire might come up with something about that using his omega skills.
Thanks for the suggestions.
Regards

[Flib]

Did all of your three Mods hell-fire, it was my first time of solder something....

And as it semms it worked very well

Have the
3.3@3.5
5@5.3
12@12.4


Bios only shows 12.3v at 12v rail, but my DMM shows 12.4v!
Under load only 12.23 in bios but sill 12.40 with DMM?Dmm shows NO Fluctations. Only between 12.37-12.42

[Hell-Fire]

Happy it worked out for you.

I would ignore what the bios is saying the flux is and rely on your DMM instead.

[Flib]

Ok! My Protection on the 3.3 rail is already on 3.8v....
But 3.6v will be enough I think.

That was an exellent guide! Thank you!
Only negative was that it costed so much time *lol* A really marathon-mod as you would say ^^

[Jesus]

One stupid question is teh Voltage in the Molex equal to the one that the ATX connector sends to the MBO?

Just checking cause I'm having a debat with a friend of mine at teh moment he claims that theres a difference and that teh readings that you get forom the Multimeter in the Molex are differnt from those in teh ATX.

[Hell-Fire]

Originally posted by Jesus
One stupid question is teh Voltage in the Molex equal to the one that the ATX connector sends to the MBO?

Just checking cause I'm having a debat with a friend of mine at teh moment he claims that theres a difference and that teh readings that you get forom the Multimeter in the Molex are differnt from those in teh ATX.

There will/may be some difference, but we are talking about in the area of the hundredths place here. My molex shows 12.30v and the ATX shows 12.28v. Same for the 5v and 3.3v rails.

The molex connectors will be slightly higher than the ATX connection.

[Jesus]

OK, Cause MBM is reading 11,98 w. 1,375 VCore and 11,86 w 1,75 Vcore while the Multimeter gives ~12,3, it fluctuates more teh f.a., teh Antec 350W but compesates it with higer woltages.

[Flib]

Same Problem, MBM5 is showing other volts and they fluctate a lot more then the ones from the multimeters.

But can you say that the volts on the molex from multimeter and the ones of the atx connecter are equal under load?

Cant believe that I have nearly no fluctation on the Molex Connecters!

I have got an idea... what about checking the reading points on the mainboard by multimeteR? I think the mainboard tries to measure these points too und shows them in bios!

[Jesus]

The winbond chips measure the voltages, I have a voltage drop of ~0,03-0,05 on load.

[Hell-Fire]

Yes, check them on the board as well as the ATX connector. Be careful not to cause a short circuit.

MBM reads them off the board.

[Flib]

measured on the molex with dmm, on the board with dmm und noticed what mbm5 is saying - here are the results (couldn#t do it for 3,3V,don't know the reading point on my board - an35n ultra)

Molex: 12,40
Board: 12,32
MBM5: 12,30

Molex: 5.30
Board: 5.24
MBM5: 5.30

this is in idle mode! Cant give any results under load atm, because my system isn't stable! (Motherboard isn't working properly)

[Hell-Fire]

The AN35N boards are notoriously hot natured.

Heat could be keeping you from being stable. I would check the SB, and the FETs to see if they are getting hot.

[Flib]

mosfets are ok but sb is getting really hot. Cant hold my finger on it for more than 5 seconds

Noticed a strange thing:
When i don't plug in the 12V Connector to the board, MBM5 only shows 11,8 and DMM 12,0V on board! Why so low? Thats a drop of 0,4Volts in IDLE Mode!

This board sucks! Looking for an Infinity or an Abit

[Hell-Fire]

Well, when you unplug that connector, you are without 2 12v inputs.

You are on the right track with either the DFI or Abit.

[Mod_Evil Br]

My friend,

This mod it serves to my thermaltake font, this one TT420AD, i have that modification of 3.3 sense lines, in now i want mod the 12 and 5 v lines too.

[Alexius H [SLO]]

Hi!
I'm about to vmod my Antec TP430. Will be this ok:
10ohm resistor + 1kohm VR ----> 3.3v line
22ohm resistor + 2kohm VR ----> 5v line
47ohm resistor + 5kohm VR ----> 12v line

Thanks for answers!

[Hell-Fire]

Yes, that should work as well.

Be aware that starting with the lower resistance VRs will boost all the lines above spec and you will not be able to get back to spec rails if you so desired.

That is mainly a point of interest if you are wanting to run the 5v and 12v rails within 10% of spec. Some drives do not respond well to the high 12v rail.

I would recommend using a 5k VR on both 5v and 12v rails.

[Alexius H [SLO]]

Allright, 5k for both it will be. I hope this is the best possible combination, what do you think?