Why is my 5V so low? Read this

[freshy98]

Well, found out what NOT to do... It scared the living daylights out of me, and it was night!

I tried to use the multimeter, but somehow due to my not to steady hand I accidently touched another pin of the mosfet.
Thus creating a link between the gate and an anode or kathode.
My system was of in a flash! (not a real one).
restarting wouldn't work, so I waited a while. Still nothing.
Then I cleared the CMOS and luckily everything worked again
So I didn't fry my mobo
It's working happily now again, but learned my leasson.

be carefull!

 

[Tiger]

I have had 5V problems ever since I built this system, ( sig below) and am now on my 3rd PSU. Macron 300W ( 30 days), Fortron 300W (60 days) and lastly the Enermax ( about 4 months). The Enermax 5V has slowly slid downwards and am now having stability and startup problems. Have been in touch with MSI who blame Enermax and have been in touch with Enermax who said that I was not having any problems at that stage but to contact them agian if I did. Have contacted them and now awaiting a response.
I have tested the MOSFETS on my MSI K7T Turbo Raid V3.0 and for those who are interested the pic below shows the relevant ones (4 in all). If you use this info check your mobo first. I don't take responsibility for mistakes. The other MOSFETS were all giving readings of +-2V. I haven't done the mod yet. Waiting to see if Enermax have suggestions before I resort to that.
Hoot is it okay to take a single connection for all 4 from a molex connector? I have molex connectors for fans and thought of just joining all 4 wires and connecting via one of these molex connectors.

 

[Hoot]

The more dedicated conductors going to the MosFets, the less the drop through them. That, having been said, use as few as possible to get the job done. I'd start with one and see how it goes. Only add more if, for some reason, one did not cut it. Keep it simple.

Lets say that your Enermax puts out 5.1V under load, as measured at one of the unused Molex connectors, but you're only seeing 4.75 at the MosFet. If by adding one 5V booster wire, your voltage at the MosFets goes up to 5.0V. It would be a waste to add three more 5V booster wires to just to get it up to 5.05V. More wires equals more opportunity for an error.

Hoot

 

[Hoot]

No suggestions on how to get the wires attatched to the stump of the pins?? Anyone know of any clamping pamona grabbers that will hold onto the entire transistor package or such?

I've been stretched pretty thin lately and only now saw all the posts that need addressing.

Some core regulators use 3 MosFets per leg and some use only 2. By leg, I mean that of all the MosFets in the core voltage regulator, half of them switch the plus side of the signal and half switch the ground side. I don't want to go into a big explanation of that design, hence the simple explanation. You only want to supplement the plus half of the signal path. There are plenty of paths on the ground side already.

If you don't feel comfortable soldering to the center "stubs" of the plus side MosFets, the Tab of them, that is soldered to the motherboard is the same connection. Inside the MosFets, the center pin is connected to the Tab. IE They are the same connection.

Hoot

 

[Hoot]

Re: What do you think?

I checked out my system , I hooked up the multitester like this. one lead going to a blk wire from one of my drives and the other lead going to the center lug in the mosfet. I had 5.09volt's. I then played a music cd and put a dvd movie in and them ran 2001 mark and it went down to 5.02 .I am a electrician (Building's) but I think from what you guys are saying that is good and needs nothing, no mod like hoot did is needed. I have a Aopen Case and power supply 300 watt. What do you all think????

For the most accurate measurement of the +5V at the MosFet, the meter minus lead would best be placed on a point on the motherboard that corresponds to ground, preferably as close to the MosFets as convenient. There are plenty of access spots. Yes that should be the same as the case or even a black lead on one of the Molex connectors, but with such high current flowing, the further away you are from the area of the motherboard where the MosFets are mounted, the greater the chance of inaccuracy.

Hoot

 

[Hoot]

Hi,
I have taken some voltage measurments from my system, and i was wondering if i would benefit from this 5v mosfet mod. My system specs are: 300W psu, Abit KG7, Tbird [email protected] (9x137)
Here's the volts info:

Looking at your graphic, if your PSU has an internal trimpot for turning up the +5V output, you should adjust it to ~5.1V at idle.
Then recheck your readings under the different scenarios. If the voltage measured at an unused 5V line on a Molex still drops to below 5V under load, chances are your particular PSU is running at or very near its capacity. At that point, you have to accept that fact and live with it, or buy a higher capactity PSU.

Hoot

 

[Just shoot]

Hoot you did a very good job of writing this but I guess I'm alittle confused as why wouldn't you recrimp the connections on the atx connector to ensure a good connections before voiding your warranty on a good O/C Board. This should only be used if after testing with a multimeter that you cannot get a good connection at the atx connector and the recrimping doesn't work.

I had found this when I replaced my 300 watt PSU to a 400 Watt Psu that the atx connector was a little sloppy (and 5 volt rail still hung around 4.8 volts at load) so I just took a eye glass screw driver into the female side of the atx connector and closed the spade back up on all and wala voltage at mosfets 5.07 under full load and 5.1 at idle.

Granted this won't fix all the connectors as being the weak link but it should rule out most of them.

 

[Hoot]

That's an excellent idea, but very technique sensitive. You, obviously have the technique down, as do I and I'm sure some other technically inclined people, but for the majority of the users, its hard to say. You can take that technique too far and disfigure your pins. Then when you try to undo it, they break off or become more disfigured. You know what I mean. I've had 30 years, in electronics, to do it wrong and learn how to do it right the second time.

Hoot

 

[Just shoot]

Yes, you are right patience is a virtue, and ignorance just takes longer. LOL

 

[eobard]

I've been stretched pretty thin lately and only now saw all the posts that need addressing.

That's what happens when you do a good job on something that a lot of people can use. I can think of worse problems than being compotent.

If you don't feel comfortable soldering to the center "stubs" of the plus side MosFets, the Tab of them, that is soldered to the motherboard is the same connection. Inside the MosFets, the center pin is connected to the Tab. IE They are the same connection.

Hoot

Comfort isn't the issue, capable is. I'm just too ham fisted to make it stick but I do have an idea on what to do. As for using the tab/backing of the transistor they are not really an option. Most "TO-220" transistors I've seen have a length of metal with a hole in it to allow the transistor to be screwed to a sink for a tab but the MOSFETS in my board barely have a ridge of 2mm coming off the top, no screw hole or anything else to get a good solder conection.

I've had 30 years, in electronics, to do it wrong and learn how to do it right the second time.

Hoot

I don't suppose you could help me try to fix my monitor could you? The red is gone on it so I'm thinking it's probably the red gun but I'd hate to give up on it if it's only a $2 chip that's giving up. I'm pretty sure I've got the physical skills (in spite of my ham fistedness) and base electronic knowledge to make repairs if I knew what repairs to make but I don't. If you actually do have any ideas I am willing to hear them.

btw: I've done the "shake the cable" thing and the "dust it out with compressed air" thing already.

 

[Hoot]

Most monitor manufacturers don't give out schematics and without a schematic, you may as well turn off the lights and just throw darts at the circuit card. Even I won't touch a monitor without a schematic. I could have had a 17" Sony Trinitron for free from work. It had lost its Red also. I putzed around with it for an hour, trying the obvious things, but no revelations. So, it went back on the recycle skid. Sounds like yours is headed that way also.

Hoot

 

[eobard]

I finally hooked mine up. It has apparently yeilded no benefit, although I'm runing at 1155mhz my 5v has dropped to 4.813v, a voltage level that has caused my system to stall before. Still, it hasn't stalled yet. Should I no longer trust my 5v readings as reported by PROBE? Does this mod bypass the sensor?

 

[eobard]

Well I've rebooted from my crash. Well it was worth a try. Got to 1102mhz though, upped the resistance on my volt mod, core voltage went down a bit, 5v line went up a bit. An acceptable trade.

 

[freshy98]

I was thinking. (yes, I can...)
Since soldering would leave you with the troubles of removing the motherboard when needed, I have this idea.
Why not solder wires to the gates of the mosfets you need to mod and wrap them together at the end and solder it.
Then, take something which is able to connect and disconnect. Like molex connectors, only different.
I'm sorry, my English is OK but I don't know every word out of my head
When I'm visiting my parents I will make the stuff and take some pictures of it.

Reason for this idea is that soldering the wires permenantly isn't a real option because of the troubles removing the motherboard which tweakers do.
And secondly is that getting a grabber like Hoot shows on page 6 is almost impossible to get here in The Netherlands.
Thirdly, soldering the wires to the gates of the mosfets is better in my opinion. Offcourse, the connection between the wires coming from the gates and the wire coming from the PSU are linked together in the middle which could cause problems, but I think this will be better in general.

Let me know what you guys/girls think about it.

freshy98

 

[eobard]

I was thinking. (yes, I can...)
Since soldering would leave you with the troubles of removing the motherboard when needed, I have this idea.
Why not solder wires to the gates of the mosfets you need to mod and wrap them together at the end and solder it.
Then, take something which is able to connect and disconnect. Like molex connectors, only different.
I'm sorry, my English is OK but I don't know every word out of my head
When I'm visiting my parents I will make the stuff and take some pictures of it.

Reason for this idea is that soldering the wires permenantly isn't a real option because of the troubles removing the motherboard which tweakers do.
And secondly is that getting a grabber like Hoot shows on page 6 is almost impossible to get here in The Netherlands.
Thirdly, soldering the wires to the gates of the mosfets is better in my opinion. Offcourse, the connection between the wires coming from the gates and the wire coming from the PSU are linked together in the middle which could cause problems, but I think this will be better in general.

Let me know what you guys/girls think about it.

freshy98

That's what I did. It is a trade off. It upped my 5v but not by much. But it was enough to let me get to 1102mhz stable. The slight boost allowed me to set my core volt mod to 1.94v and my 5v line was running no lower than 4.857v, which is just good enough. I got half of what I wanted. I think if I had soldered the connections on to the mosfet I may have gotten to 1150, or even 1200 stable. mmmmmmm 1200!!!!

 

[Voodoo Rufus]

I did something similar for my board. It didn't need extra voltage, but the Molex ATX connector melted, caused by the red ATX wires getting so hot that they burned apart. My father and I cleared some of the plastic on the back of the motherboard PCB to expose the copper plate that provided the power to the mosfets. We used two 13 gauge wires soldered to that plate and used a 2-pin Astroflight gold connector to bypass the ATX connector so that we were able to supply power to the proc.

All I think of that went wrong was a too small contact patch for the poewr connectors for the power that was going through them, or bimetallic corrosion accelerated by the current flow.

Instead of using another Molex POS connector for these mods, something even better would be to use any hobby/radio control connector from companies like Deans or Astroflight. They can easily handle 50 amps per pin.

Are the red wires on ATX connectors 5V or 12V? It would make sense for them to be 12V I would think.

 

[eobard]

The red is 5v, the yellow is 12v. I agree that the red would make more sense as 12v. Red is the danger color, yellow is the caution color. Neither 5 nor 12 volts will kill you but 12v is (microscopically) more likely to.

 

[Voodoo Rufus]

There would be less electrical resistance to use the 12V line to power the CPU, especially with the small wires they use for the connector.

 

[Ichelo351]

the color doesn't really have to do with danger to a person, like 5 or 12 volts would do very little to a person. it has to do with the sensentiveness to the computer, the 12 v line is the "rough" current, the only thing it is used for in the computer is really to power fans and motors. and thus if you watch the +12 v line, it isn't very stable or exactly at 12 v. less monitoring or filtering is on the 12 line because it is just for motors and fans which will not have major problems with "rough" current, so its "caution". while the +5 v line runs pretty much everythig else, all the expensive stuff that if it had "rough" current it could potientually die. so to the computer, the +5 v line is the dangerous one, because if somethign happens to that, like it being spiked with something it would have worse effects than with the +12 v line. at least thats how i know it, if that makes sense.
hoot, that is a great piece of work, i may do that at some point, because right now my +5 is down alittle, but also my +5 is down from the molex but not as much. i am suffering from a sucky power supply problem, a barely 300 watt total generic, but it is atleast alittle better than my old 250 watt one! i am hopfully getting a nice 410 watt one that will last my long time, then do nice mod to it hehe.
-Aaron

 

[pa1983]

I have a epox 8KHA+ and there are 3 mosfets on top of the board and 3 mosfets at the back side of the motherboard. Is the mosfets on the top or on the back that I am suppose to connect the +5 cable?