Badcaps.net Forum
Go Back   Badcaps Forums > Welcome to the Badcaps.net Tech Forum! > Frequently Asked Questions (No Posting)
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 06-14-2008, 11:31 PM   #21
andlcs
Member
 
Join Date: Feb 2007
Posts: 22
Default Re: Testing VRMs

Quote:
Originally Posted by badman86
Hi!
It's an MSI K9A. I'd like to measure the resistance from the input and output of VRM to ground.
I think you can measure the input at the toroid coil near the ATX+12V conector.
And the output at the shielded inductor near the CPU socket. I'm not sure tho...

power off your computer first
andlcs is offline   Reply With Quote
Old 06-21-2008, 06:19 AM   #22
badman86
New Member
 
Join Date: Jun 2008
Posts: 3
Default Re: Testing VRMs

Thank you for your answers, I think i got it now!

Now, what is not clear yet is this:

a. Measure resistance from power supply pin (+3.3, +5, +12, -5, -12) to input of VRM. Resistance should be zero (too low to measure).

Power supply pin means the ATX connector on the motherboard?
badman86 is offline   Reply With Quote
Old 09-02-2008, 07:29 AM   #23
coolday
New Member
 
Join Date: Jul 2008
Posts: 12
Exclamation Re: Testing VRMs

Admins and moderators please try to start a section on motherboard repairing. it would be very helpful for newbies like us. Maybe this would be the first website to do so.

coolday is offline   Reply With Quote
Old 11-20-2008, 06:15 AM   #24
coolday
New Member
 
Join Date: Jul 2008
Posts: 12
Default Re: Testing VRMs

so anyone can provide pictures .... it would help us a lot
coolday is offline   Reply With Quote
Old 12-14-2009, 04:48 AM   #25
closetonanak
New Member
 
Join Date: Dec 2009
Posts: 1
Default Re: Testing VRMs

First You Should Know Where Is Vrm Section On Board And How It Works, Which One Is Positive Line And Negative Line Then Mosfets Of P And N Lines, Check The Voltages, If No Voltages Means May B Mfets Are Open Thn Take Them Out From There Place And Check Also Check On Pads If Still There Shorting Means May Be Another Mosd\fet Has To Take Out From Board And Chk It Like That Go Ahead If U C That Capacitor Is Leak So Fst U Hav To Repalce, And In Ths Case Pwm Ic Of Both Line ( +, _ ) Have To Replace And Chk, Buck Control Ic( For Power Good Signal) , Io All Thing Should Be In Lone To Replace
closetonanak is offline   Reply With Quote
Old 12-26-2009, 10:51 AM   #26
sam67
Badcaps Veteran
 
Join Date: Dec 2009
City & State: uk
Posts: 250
Default Re: Testing VRMs

Quote:
Originally Posted by coolday
so anyone can provide pictures .... it would help us a lot
Would also like some pics if anyone has any or links ..This is really interesting and should be further explored ..
sam67 is offline   Reply With Quote
Old 01-08-2010, 01:48 PM   #27
alexanderjohn
New Member
 
Join Date: Dec 2007
Posts: 2
Default Re: Testing VRMs

yes! especially laptop motherboards
alexanderjohn is offline   Reply With Quote
Old 01-24-2010, 09:04 PM   #28
Pyr0Beast
Badcaps Veteran
 
Join Date: Feb 2009
City & State: Slovenia
Posts: 406
Default Re: Testing VRMs

Laptop motherboards ... hmm.... if I have the time ...

//c. Measure voltage at the input to the VRM (+3.3, +5, +12, -5, -12). Anything less than the value obtained in step 6.b indicates a high resistance in the PC board traces to the VRM, and is probably not repairable, even with a schematic.//
Is repairable, by making a bridge with a wire. Usually from one capacitor to the next one. Never occurred to me unless it is a manufacturer design.

Basically, it is pretty simple. If mainboard does not POST, check voltages.
If PSU voltages are within range, check voltages on motherboard. Cpu has pretty much standard voltage. About 1.4V is fine for newer CPUs, 1.8V for athlons and P3's, 2V or greater for first celerons and P2 (Some early P3)
If there is no power (voltage) to the CPU, check if you placed capacitors the right way, observing the polarity. Same goes for other circuits, RAM, AGP etc. ..
If VRM IC is busted, it would be hard to find a new one. Sometimes (rarely) only one of the mosfets break, usually the upper one. When it does that, the lower one migh go 'poof' as well (protecting the CPU).
If one breaks, replace both. Check IC for damage, might be good to replace that one as well, sometimes it is the cause of this mess.

//VRMs (voltage regulator modules) are a specific class of MOSFETs; //
Far from being true. A VRM module consists of the controlling IC and MosFet's (if we focus only on semiconductors).
However, it is true that there are many type of FET's. Mosfet being the most common one. JFET is one of the other type.
Pyr0Beast is offline   Reply With Quote
Old 01-29-2010, 11:42 AM   #29
ivanlee05
TipidPC.com
 
Join Date: Nov 2009
Posts: 6
Default Re: Testing VRMs

Source = Input
Drain = Ground
Gate = Output

__________________
ivanlee05 is offline   Reply With Quote
Old 01-29-2010, 11:50 AM   #30
Pyr0Beast
Badcaps Veteran
 
Join Date: Feb 2009
City & State: Slovenia
Posts: 406
Default Re: Testing VRMs

?
Source = Output
Drain = Input
Gate = Gate

Current flows from the Drain to the Source afaik. (When the gate is (ON))
Can also flow backwards once the gate is on, however, the body diode will conduct when the gate goes off, leading to rapid heating.
Pyr0Beast is offline   Reply With Quote
Old 01-29-2010, 07:57 PM   #31
ivanlee05
TipidPC.com
 
Join Date: Nov 2009
Posts: 6
Default Re: Testing VRMs

Quote:
Originally Posted by Pyr0Beast
?
Source = Output
Drain = Input
Gate = Gate

Current flows from the Drain to the Source afaik. (When the gate is (ON))
Can also flow backwards once the gate is on, however, the body diode will conduct when the gate goes off, leading to rapid heating.

thanks sir for the explanation sir... i have a motherboard with no power here, i already check every parts like processor, memory and psu, they are good.. i'm suspecting dead vrm...
ivanlee05 is offline   Reply With Quote
Old 01-29-2010, 09:31 PM   #32
Pyr0Beast
Badcaps Veteran
 
Join Date: Feb 2009
City & State: Slovenia
Posts: 406
Default Re: Testing VRMs

Check the output voltage then.
(With the component in place of course)
Pyr0Beast is offline   Reply With Quote
Old 01-30-2010, 03:52 PM   #33
ivanlee05
TipidPC.com
 
Join Date: Nov 2009
Posts: 6
Default Re: Testing VRMs

I am having problem with my neighbor's PC... His motherboard (Biostar GF7050V-M7 SE) could not boot... It has a power but theres no display or even beeps... I already check all of the VRM mounted in the Motherboard, all does have output voltage that range more or less what the input voltage is...

My first tought was a Failed BIOS updates... But He doesn't even know how identify a computer parts... I still had to recover the BIOS thru AMIBOOT.rom BootBlock Recovery... No, the problem is not the BIOS...



Other components like ram, psu, hdd, odd and the processor has been verified in my PC except for the video card... He doesn't have any, He uses the Onboard Video...

Thanks for those who will reply...

Last edited by ivanlee05; 01-30-2010 at 04:02 PM..
ivanlee05 is offline   Reply With Quote
Old 01-30-2010, 04:35 PM   #34
ivanlee05
TipidPC.com
 
Join Date: Nov 2009
Posts: 6
Default Re: Testing VRMs

I think this is a chipset problem that I could not repair anymore... I went to test all the electrolytic capacitor, and all does have more or less same voltage as input voltage...

I have no time to check all the surfaced mount resistors, diode and capacitors... I'll just force him to buy another Motherboard...

His motherboard served him well for almost 3years...

R.I.P. Biostar "RedFox" GF7050V-M7 SE

Bought: 09/10/07
Died: 01/29/10

^_ _^
ivanlee05 is offline   Reply With Quote
Old 01-30-2010, 04:49 PM   #35
Pyr0Beast
Badcaps Veteran
 
Join Date: Feb 2009
City & State: Slovenia
Posts: 406
Default Re: Testing VRMs

Replace the board. Simplest and effective.
Pyr0Beast is offline   Reply With Quote
Old 02-09-2010, 01:31 PM   #36
Zero Hour
Getting there
 
Join Date: Oct 2009
City & State: Brandon, MS
Posts: 31
Default Re: Testing VRMs

I suggest sir as a last ditch effort before retiring it completely if it's not too late, baking the board. I have the problem as a common issue with geforce 6100/6150 chipsets. It's the closest I can get easily to a 'bga reflow' since I don't have a heat gun or a torch or patience. I know it's not a 'convenitonal' method, but for a board you've attempted everything else on and are set on pitching it, it can't hurt.

My method, strip the board of any heatsinks and battery and cmos chips if possible, remove all thermal paste and thermal pads, preheat oven to 384F, elevate the motherboard off of a pan (i ball up aluminum foil and leave a little pointy end for 4 mounting holes to support the board) and bake for 5 minutes. I don't suggest pushing past 6 minutes, it's never been beneficial in my cases and stinks like hell >.< But so long as you can vent the house afterward hey it's fun :P

Or if nothing else, I'd pay shipping on the board if you don't wanna go through the trouble of baking it

Last edited by Zero Hour; 02-09-2010 at 01:34 PM..
Zero Hour is offline   Reply With Quote
Old 02-24-2010, 04:46 PM   #37
cmosbios
New Member
 
Join Date: Dec 2009
Posts: 12
Default Re: Testing VRMs

well you can use hot air rework station for reflow.
cmosbios is offline   Reply With Quote
Old 02-24-2010, 04:57 PM   #38
cmosbios
New Member
 
Join Date: Dec 2009
Posts: 12
Default Re: Testing VRMs

@Akor
you mean if I test the VRM, test each mosfet(VR) inputs and outputs? I am not sure if you are referring to VRM block (2 mosfets, ic driver, pwm) input and output circuit tests. what i know about the VRM is NOT the mosfet itself but the circuit. please enlighten me.
cmosbios is offline   Reply With Quote
Old 01-04-2011, 12:12 PM   #39
styxbound
Member
 
Join Date: Aug 2010
Posts: 91
Default Re: Testing VRMs

Sorry, I'm old and senile. Can anyone simplify for me how to find the inputs and outputs on vrms? There seem to be any number of fets around the cpu on a lot of boards, and I can't figure out where the in and out is on the circuit.
styxbound is offline   Reply With Quote
Old 01-04-2011, 12:14 PM   #40
Pyr0Beast
Badcaps Veteran
 
Join Date: Feb 2009
City & State: Slovenia
Posts: 406
Default Re: Testing VRMs

Ouput is past the choke on output capacitors
Input on input capacitors
Pyr0Beast is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2018
Powered by vBulletin ®
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 08:56 PM.

Did you find this forum helpful?