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Help my A7V8X 5 Volt is very low!!!!

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rrster

Registered
Joined
Mar 10, 2003
Does any bright soul has any info on how to do 5V Mod on A7V8X.
My 5V rail on Antec SL350 drops down to 4.76 and 3.3 drops to 3.16 and 12V climbs to 12.28 according to MBM.
Machine crashes once in a while, I believe 5V rail is the cause.

I have plugged in MM to test the 5V rail and digital MM shows it good at 4.98 steady.

I have read the sticky. Any one have pictures or guides that I can follow to bump up my 5V rail on A7V8X Mobo.

I am not bright enough to do it without help. :(

rr
 
it's so because the location of a 20-pin ATX connector is so far away from power MOSFETs.
a thread in this forum on +5V line will help you.
I also did this +5V mod on my A7V8X to get 5V stable.
Just solder a thick (2.5 mm.) wire to an input inductor coil and connect the other end to +5V line.
 
Any Pictures??

krairach,

a thread in this forum on +5V line will help you.

Can You provide me a link to it. I searched the forums, but came up empty.

Can you please, take a picture of where the mosfets are. so that I can look at it and figure it out. I do not want to take any chances.


Thanks.

rr
 
It's not as much the distance from the ATX connector to the MOSFETS as it is the contact resistance across the connectors mating pins. Look at the following picture. There are two applicable MOSFETs. Either one will do, or you can put a +5V wire to each. On the MOSFETS, the tab that is soldered to the motherboard is where you make the connection to an unused +5V wire from the PSU. If that is too daunting, the center of the three pins on each MOSFET is internally connected to the tab. In MOSFET terms, these are called the Source.

Most quality PSUs have a connector that carries several voltages to the motherboard, besides the ATX. I believe these are for Intel processor boards. If you are not using that connector, it is a good source for obtaining a +5V line not normally used.

Solder well and use the actual 18ga wires from the PSU. Using very small gauge wire defeats the purpose of the mod.

a7v8x_5v.jpg


This connector:

pic04.jpg


Good Luck

Hoot
 
Thanks Hoot

I believe that pic is of actual A7V8X mosfets. Now I am feeling confident about this mod. I was concerned as your sticky said there ar 6 Mosfets and I could not find 6 of them. max was 4 the ones you have pictured. your pic matches my mobo.

one question I have does it make a difference, if I solder to all 4 or 1 of them or 2 of them?

I am going to solder small Wires to the 2 mosfets you have pictured for sure and then feed them the 5V rail as pictured in your sticky.


:D Thanks.

rr
 
Soldering Help

Hoot,
Is there some special silver link, or glue that I can use to make silver thing stick to the mosfet. I tried very hard for about 4 hrs to make the damm thing stick to the aluminum surface ("Here" surface in pic), but once it dried, it came right off with smooth surface :mad: on the silver with the wire.

I am using Radio Shack supplied Archer Silver Bearing Solder Wire with Rosin Soldering paste Flux. (i.e sticky glue sorta)

rr
 
First off, I did not get a chance to respond to your previous post. Some motherboards use different quantities in their MOSFET regulation circuits. In the case of the A7V8X, there are only two MOSFETS in the "high side" of the switching circuit. Those are the two I indicated. Do Not Use the Other Two MOSFETS! Doing so will damage the motherboard, CPU and very possibly the PSU.

On my A7V8X, the +5V measured with an accurate voltmeter at the MOSFETS, falls to 4.79V running Prime95 Torture Priority 10, This is despite the +5V being 5.00V coming out of the power supply. With the mod, the +5V at the MOSFET only drops to 4.93V running Prime95. whether that results in any gained stability is anyones guess. If the +5V fell to say 4.60V, that would be of greater concern.

Regarding your current post, the tab on the MOSFETs is not aluminum. It is tinned copper.

You need a high wattage soldering iron or Weller gun to solder to the tabs. Since they are soldered to the +5V power plane, it acts like a heatsink that wicks away a lot of the heat. A small wattage soldering pen will not cut it. That is why I mentioned using the center pin on the MOSFETs. It does not require nearly as much heat as the tab does. Soldering to the tab provides a better mechanical connection than the using the center pin. That is why I prefer to use the tab, despite the extra efforts needed to solder it.

Hoot
 
Will this work

Did a quick search on the MSN Search engine for Soldering Stuff

would this http://www.solder-it.com/solderpaste.asp#SIlver%20Paste

stuff Work???

or anything similar on the website.


Don't Feel too comfortable soldering on the middle lead.
Am afraid, what if the 5V wire rail accidentaly touches the other side rails. which might render board useless.

rr
 
5V rail Modded

Hoot,
I could not wait another day, I mustered up some courage and took the soldering iron and modded the middle leads of MOSFETS with the 5V Aux Rail. First time one of the soldered wire to mosfet came-off, but second time, I did it, after the mobo was screwed in the Case, it stayed and don't think it will fall off now.

I am getting a steady 4.84 or 4.81 on 5V rail now. It made a difference. I thought I would get in 4.9X range, but this certainly will do as well.

I also removed the extra Y-power 4-pin Molex, as I rewired all the power connectors keeping things simple and plugged all the fans to power directly from the pwr-supply, and only fan-monitor lead to ther Mobo. This thinking would reduce resistance and load on the motherboard.

Also, 3.3V rail mostly now stays steady at 3.20 or 3.22 and now and then drops to 3.18 or 3.17, and 12V rail is now at 12.22 from 12.28 before.

Thanks Hoot.
rr
 
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