Where to find 5Volt on Mobo...?

iSDn · Post by **iSDn** » Tue Jul 13, 2004 9:21 am

Hi!

I've got a problem with my Mobo. Since i broke my first BP6 i was never able to get my dual P3/1100MHz work at 100MHz FSB again(Tried 3 other BP6 boards). When i hit 90MHz i get RAM errors all the time and my systems is crashing instantly when i hit 93MHz FSB. Also my VTT is only 1,45 to 1,47 Volts. I did Yoishiros Mod and used the 5V from the ATX connector. But my power supply only supplies 4,95V on the 5V ATX line...is there any other way to get 5V volts from the power supply ??

Bye...

BCN · Post by **BCN** » Tue Jul 13, 2004 2:17 pm

mod the power supply with some pot, so you could regulate the ourput voltage....

how exactly? depends on PSU I guess...

cool your BX

Holodeck2 · Post by **Holodeck2** » Tue Jul 13, 2004 8:20 pm

get a high quality power supply, if find the traces for the 5v line in your Power supply, it's generally hooked to a pot, you can tweak that up just a little, and also remember to put a load on it before tweaking or else it'll start to fluxuate like mad

Stobe · Post by **Stobe** » Wed Jul 14, 2004 1:03 am

BCN wrote:mod the power supply with some pot, so you could regulate the ourput voltage....

I don't think the results will be satisfying if you smoke pot whilst modding.
But stuffing the PSU with pot, now there's an idea! "Cranking up the load on the machine gets you high!"

iSDn · Post by **iSDn** » Wed Jul 14, 2004 9:10 am

It's a Zalman 350W power supply.

BCN · Post by **BCN** » Thu Jul 15, 2004 7:50 pm

Stobe wrote:
BCN wrote:mod the power supply with some pot, so you could regulate the ourput voltage....
I don't think the results will be satisfying if you smoke pot whilst modding.
But stuffing the PSU with pot, now there's an idea! "Cranking up the load on the machine gets you high!"

I think what you did is just refrased it....

Holodeck2 · Post by **Holodeck2** » Fri Jul 16, 2004 12:48 am

zalmans are ok, I think they just rebadge some other brand's PSU

well time to start poking around in there I guess.
What you can also do is take the 12v line and plug that through a heavy duty 5v regulator and BAM! you got your own stable 5v without messing up your powersupply's warenty

purrkur · Post by **purrkur** » Fri Jul 16, 2004 4:36 pm

Zalmans are actually high quality PSU's and they make their own. I got a 400 W Zalman in my Athlon machine and it is whisper quiet and delivers extremely stable voltages.

I would not recommend putting the 12V output through a regulator to get a 5V output that is supposed to deliver high current. The 12V output is always rated lower than the 5V output, meaning that you don't get the same amount of current from the 12V than the 5V. The components drawing on 5V are the heavy duty ones in the computer. Put those on the 12V output with a regulator and I guarantee that your PSU will bottom out and your computer won't even start. However, if you only need a small amount of current for a single particular use then this solution will work, even with a small regulator (small current = smaller regulator).

Also, adding a pot for regulation: Where are you going to put that? On the ouput? That means your pot has to be capable of surviving 10-50 amps of current. In other words, it would be huge if you could find one

. Opening up the PSU in order to add a pot to the circuitry (maybe to control the PWM function, what do I know?) could work but it should only be done by somebody experienced who has a circuit diagram of the PSU.

In the end of the day, there is always a certain tolerance on the outputs. I am not sure what it is for the 5V output but if you really are looking for no less than 5.00 volts then using the 5 volts output may cause you issues because it is allowed to move within its tolerance levels. For this reason I don't think your problem is the .05 volt difference that you are lacking.

Your PSU could ultimately be suffering. Have you tried swapping it with another, even if it is just for a short while to see if your issues disappear?

Holodeck2 · Post by **Holodeck2** » Fri Jul 16, 2004 8:37 pm

Plugging the 12V through a regulator to output 5v shouldn't put that much of a load because conversion of 12v to 5v should be at about 85% efficency with a switching regulator. so say a 10A draw off of the 5v line would only be a 4-5A on the 12v with the loss for efficency factored in.
(note: linear regulators are evil)

Adding a pot to the 5v line would only allow him to control the voltage to a lower level.
Most PSUs already have a pot that they use to adjust the output at the factory, all you need to do to pry off some wax. and if it doesn't have them preinstalled then you can add your own, all you need to do is trace the 5v line in the psu to the regulator and then lookup the regulator pinouts and work from there

I think he's wanting to bump up the 5v line up to something like 5.1v for stability reasons, feed them slightly more juice so it'll overcome the electrical resistance but not fry it.

davd_bob · Post by **davd_bob** » Fri Jul 16, 2004 11:03 pm

Wait,
I feel like something simple is being overlooked here but I can't place it. With all the smoking pot and such I guess its no wonder Im confused.

Hyperspace what did iSDn and everyone else forget. Instead of pot, maybe he needs a cap.

iSDn · Post by **iSDn** » Sat Jul 17, 2004 6:25 am

I don't want to mod my power supply...a few months back i used a no name 280w power supply and my system was rock stable...maybe it is the caps again, but i can't find the right ones here in germany.

hyperspace · Post by **hyperspace** » Sat Jul 17, 2004 7:03 am

davd_bob wrote:Wait,
I feel like something simple is being overlooked here but I can't place it. With all the smoking pot and such I guess its no wonder Im confused.

Hyperspace what did iSDn and everyone else forget. Instead of pot, maybe he needs a cap.

Well, if my short-term memory serves me correctly, it was capacitors and PSU that were causing problems for me.