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Boosting 5v by adding regulators

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Old 06-16-03, 01:26 PM Thread Starter   #1
The Overclocker
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Boosting 5v by adding regulators


Boosting 5v by adding regulators

Warning:

I am not responsable for any damage caused by anyone perfoming this mod, do this at your own risk, this should only be attempted by people who are capable of perfoming this easilly and have had some experaince soldering.

If you would still like to perform this mod and ddo not have the skills requires, i recomend purchasing a diy kit such as a small amplifer or radio to help develop your skills, these are quite cheap and should be avalable from stores such as Maplin (in the UK) and Radio Shack (in the US)

Problem:

I have a very old motherbaod in my computer, it is an Abit KT7A, i still use it because i have very good ram that can do 170MHz Cas 3 or, as i usally run it - 160MHz cas2, this motherboard also supports the new Barton core (last time i checked) In addition i have no money, so i canot afford to purchase a motherboard and DDR ram at the same time, or even on their own!

This motherboard was not designed for the newest Processors and Graphics cards, and these draw more power then the motherboad can provide, this causes the 5v line to fluctuate. This is not just for this motherboard and all older motherboards and some new motherboards still have this problem.

The Solutions:

There have beeen a few solutions suggested so far, the most common one being taking a spare 5v cable and attaching it directly to the gate of the 5v regulating MOSFET's to provide additional power, however the motherboard smooths and regulates the 5v line, the 5v that is being given to it has lots of noise which is responsable for crashes.

another idea would be to increase the capacitance of the smoothing capacitors on the motherbard so that more power can be stored - allowing more to be delivered when needed (this is when the 5v line goes down) so the line wouldn not fluctuate as much.

However, i chose a different way.

5v regulators are avalable at every electronic shop such as Maplin (in the UK) and Radio Shack (in the US) they cost very little and are very effective and taking a higher voltage down to 5v.

i chose to regulate 12v down to 5v to deliver to the MOSFET's this is because when the 5v regulator is in the circuit shown below, it is very effective at keeping 5v very clean thus reducing the ammount of crashes and preventing the 5v from fluctuating.



for this purpose C1 should be above 470uf (i used 2200uf) and the voltage rating should be above 12v (common values are 16v and 25v) i used 16v as there is no need for a greater value as i don not think the 12v line it is being provided with will change uch, if it does it will case much more dammage then just a capacitor expoding.

C2 is for additional smoothing and can be a film capacitor or ceramic, i used a 100nf (0.1uf) ceramic but any value between 10nf (0.01uf) and about 1uf is fine.

i took the 12v line off the back of the motherbard where it connects to the motherboard connector, it was then routed to the front though two holes (shown in the picture below)



i then soldered the regulators directly to the pins of the MOSFETs this reduced the resistance so the voltage is closer to 5v, i used one regulator per MOSFET and each regulator had a smoothing capacitor even though the eletrolytic capacitor was shared between them.



please make sure that the electrolytic capacitor is the right way around.. something i supidly overlooked untill i had put the motherboard INSIDE the case.
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Old 06-16-03, 02:10 PM   #2
pauldriver
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ummmm, WOW.

Hardcore 'remodding' at it's finest.
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Old 06-17-03, 12:50 AM   #3
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For those of us who are a lot less hardcore (or a lot less skilled), how about getting a PSU with remote voltage sensing on the +5V as well as the +3.3V and removing the +5V sense wire from the ATX connector? Then connect this wire right where the +5V feeds the onboard votlage regulator.

Unfortunately, most PSUs don't have remote sensing except for the +3.3V. I think that Antec TruePowers do, and SmartPowers are built for it but don't have the wire installed. Some Deltas have it.
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Old 06-17-03, 06:22 AM Thread Starter   #4
The Overclocker
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Quote:
Originally posted by larrymoencurly
For those of us who are a lot less hardcore (or a lot less skilled), how about getting a PSU with remote voltage sensing on the +5V as well as the +3.3V and removing the +5V sense wire from the ATX connector? Then connect this wire right where the +5V feeds the onboard votlage regulator.

Unfortunately, most PSUs don't have remote sensing except for the +3.3V. I think that Antec TruePowers do, and SmartPowers are built for it but don't have the wire installed. Some Deltas have it.
one of the problems with this, appart from the requirements for the powersupply, is that the 5v line direct from the psu is still quite 'noisy' and can cause crashes, the reason i used 5v regulators with smoothing capacitors is to make the 5v line i was suppling to the MOSTFET's much 'cleaner' and helping to reduce the crashes.

i assure you this isn't as hard as it looks, if you are careful, i also plan to increase the smoothing capacitor as i still get the5v line changing a bit (it is always between 5.00v and 4.98v but i would always like it on 5.00v) this is dont by increasing C1 which at the moment is 2200uf, i will try and get about 10000uf on it. i may also increase the large capacitors on the motherboard around it as these do the same thing, a higher value will result in less fluctuation.
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Old 06-17-03, 11:24 PM   #5
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Nice mod.

You're using the 7805s, correct?

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Old 06-18-03, 03:43 AM Thread Starter   #6
The Overclocker
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Quote:
Originally posted by Daemonfly
Nice mod.

You're using the 7805s, correct?
yes, i have considered using others as i do have access to more then that but i did not require a low voltage drop out as it was being fed with 12v, and i did not feel that they would require more then 1A (they are probably nt getting that as the voltage regulator is not heatsinked)
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Old 06-18-03, 10:59 PM   #7
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Yeah, you're just giving it a bit of a boost so you shouldn't need anything more powerful. If you find they do warm up under heavy load, heatsinks would cure that.

I'm considering doing this to my Albatron board, which has crappy 2-phase power and could REALLY use some power circuit work.

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Old 06-19-03, 01:44 PM Thread Starter   #8
The Overclocker
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Quote:
Originally posted by Daemonfly
Yeah, you're just giving it a bit of a boost so you shouldn't need anything more powerful. If you find they do warm up under heavy load, heatsinks would cure that.

I'm considering doing this to my Albatron board, which has crappy 2-phase power and could REALLY use some power circuit work.
well if you need any help with anything i can offer advice, i can also send you some regulators if you want, if you do need more power then i recomend using a pnp transistor to boost the current handeling. if you need a scematic then tell me.

im considering increasing the capacitors on the motherboard as well, which should furver increase stability, you may want to try this instead or as well if you can get capacitors the right dimentions

to repete the steps in finding the right MOSFET's for others - witha digital mulimeter (can be found very cheap) set to the right voltrage rating (should be 20v) and conect the black lead to ground (put it into the black wire on a spare 4 pin connector) and with the red lead touch the tab of the MOSFET to check the voltage, test the MOSFET's neer large capactiors.

Last edited by The Overclocker; 06-19-03 at 03:04 PM.
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