Announcement

**i4004** · 05-11-2009, 04:41 PM

Re: VIA EPIA ML Mainboard no longer powers-up

yes, on mobo they can be bad even if they look ok.
they go high in esr, not really SC or open circuit.

>Checked the power rails using a reasonably inexpensive PCI Post Card and only the +3.3volt rail is powered-up however a transistor/voltage regulator nearby the BIOS gets extremely warm.

that fet should be checked.
if you have continuity (check with usual multimeter) in most combinations you try it's probably a toast...
follow these instructions
https://www.badcaps.net/forum/showth...=fet#post68763
caps should be checked too, as fets usually go BECAUSE esr was too high...

**newbie2linux** · 05-11-2009, 04:57 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by i4004

yes, on mobo they can be bad even if they look ok.
they go high in esr, not really SC or open circuit.

>Checked the power rails using a reasonably inexpensive PCI Post Card and only the +3.3volt rail is powered-up however a transistor/voltage regulator nearby the BIOS gets extremely warm.

that fet should be checked.
if you have continuity (check with usual multimeter) in most combinations you try it's probably a toast...
follow these instructions
https://www.badcaps.net/forum/showth...=fet#post68763
caps should be checked too, as fets usually go BECAUSE esr was too high...

Hi,

Thank you for your reply. Much appreciated. Just so that I've interpreted this correctly regarding the high esr that you have mentioned does his basically mean that faulty electrolytics generally have a very high resistance whereby they're acting like a resistor rather than a capacitor?

Not 100% on how to go about testing whether the transistor/voltage regulator has gone faulty however would not be surprised if it's cooked itself as it was almost impossible to touch due to the amount of heat that it was generating. At a guess something has caused the transistor/voltage regulator to go faulty and this could have been due to faulty capacitors possibly due to some other fault I'm really not sure.

Need to read the URL that you've provided.

Anyway would you recommend that the electrolytics are replaced as the mainboard hasn't had a lot of use?

Thank you.

**i4004** · 05-11-2009, 05:23 PM

Re: VIA EPIA ML Mainboard no longer powers-up

>Hi,
>Thank you for your reply. Much appreciated. Just so that I've interpreted this correctly regarding the high esr that you have mentioned does his basically mean that faulty electrolytics generally have a very high resistance whereby they're acting like a resistor rather than a capacitor?

esr explanation
http://en.wikipedia.org/wiki/Equival...ies_resistance
it's not resistance you can detect on usualy meter...it is measured with esr meters and these use AC to pass thru the suspicious cap, and then it's series resistance can be measured...

numbers are not high...1ohm is usually too much for mobo use...but it can be less...
it can be 0.25ohm and be faulty, depending on the mobo design...

what happens is that they're not conducting noise and ripple to the ground when their esr rises...and this strains semicoinductors, eventually it kills those fets etc.

one esr meter
http://www.anatekcorp.com/blueesr.htm

testing; few first links here
http://www.google.com/search?hl=en&q...sting&aq=f&oq=
and that previous link

>Anyway would you recommend that the electrolytics are replaced as the mainboard hasn't had a lot of use?

i wouldn't change the lytics untill i'm sure fets are ok, because if they're not it means you'll be chaning caps first, and changing fets later...
(also, when fets die there are no guarantees some other semicinductors are not fried too, as these fets supply the whole mobo with current)
i would first check the fets, then check esr of caps and that would provide data...

if you don't have esr meter for the caps then you can still check fets with multimeter...
most of the time badcaps will bulge...
https://www.badcaps.net/pages.php?vid=5
but again, it's not a law...they can look ok and be crap...

if you tell us which caps are those (what do you see on them) or if you photograph them and put pix here, we'll be able to tell you what are the chances of those caps prematurely dying...

**PCBONEZ** · 05-11-2009, 05:49 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Many of the VIA EPIA boards had caps problems.
Some used Chemicon KZG which go bad without bloating.
Some had Nichicon HM and HN which were bad [defective] from 2001-2004 but those usually bloat.
I wouldn't be surprised if some used OST which can also go bad with no bloating.
-
A photo I found of your board looked like it had Nichicon HN on it.
~ But it wasn't a great photo.

**PCBONEZ** · 05-11-2009, 06:20 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by newbie2linux

Just so that I've interpreted this correctly regarding the high esr that you have mentioned does his basically mean that faulty electrolytics generally have a very high resistance whereby they're acting like a resistor rather than a capacitor?.

To the Ripple Voltages [frequencies] they are supposed to be passing to ground [filtering out],,,,
- Yes, you have the general idea.

When the ESR goes up the caps aren't sending as much noise to ground which means the noise is making it's way into other circuits.

**MegaOne302** · 05-11-2009, 06:43 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by PCBONEZ

To the Ripple Voltages [frequencies] they are supposed to be passing to ground [filtering out],,,,
- Yes, you have the general idea.

When the ESR goes up the caps aren't sending as much noise to ground which means the noise is making it's way into other circuits.

Quick qustion, I understand that a high ESR on a motherboard cap can be bad, but can a caps ESR ever be too low (besides a short)?

**kc8adu** · 05-11-2009, 07:35 PM

Re: VIA EPIA ML Mainboard no longer powers-up

no.but you can come to a point where even the best ultra low esr caps make no difference as the traces become the limit.
and a pic of that fet and the area around it will help.

**MegaOne302** · 05-11-2009, 08:01 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Thanks for the quick reply kc8adu; I'm still learning...

**newbie2linux** · 05-12-2009, 10:12 AM

Re: VIA EPIA ML Mainboard no longer powers-up

Hi to all that have responded to this thread and thank you for your suggestions. Every effort will be made to post some photos late this evening.

Having quickly checked the mainboard again I've noted the following:-

1. The two largest capacitors, 1500uf, 10v have the Chemicon logo on. These are adjacent to the ATX PSU connector.

2. The other larger capacitors, 1000uf, 6.3v are all Nichicon electrolytics.

3. The part number on what we think is a FET is APL1084 WHCDW (Q9 on mainboard).
Cannot remember for certain whether it was Q8 or Q9 that was very hot whilst power was applied to the mainboard. Neither are showing any signs of damage externally and the PCB isn't damaged either thankfully however at a guess the FET(s) could be damaged. The part number on Q8 looks like AMS1117 2.50723 however this is smaller than Q9 and the part number is very difficult to read.

Interesting subject this. Would like to get this mainboard working again however cannot afford to buy a dedicated FET nor Electrolytic / ESR tester. Am happy enough with recapping capacitors that are suggested to be replaced however at a guess the FET(s) are going to be a lot more difficult to replace as they are surface mounted. Any further suggestions / help would be appreciated.

Thank you.

**PCBONEZ** · 05-12-2009, 11:47 AM

Re: VIA EPIA ML Mainboard no longer powers-up

You can get APL1084 spec sheet here.
http://www.anpec.com.tw/searchProduc...eyword=APL1084

**newbie2linux** · 05-12-2009, 05:03 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by PCBONEZ

Many of the VIA EPIA boards had caps problems.
Some used Chemicon KZG which go bad without bloating.
Some had Nichicon HM and HN which were bad [defective] from 2001-2004 but those usually bloat.
I wouldn't be surprised if some used OST which can also go bad with no bloating.
-
A photo I found of your board looked like it had Nichicon HN on it.
~ But it wasn't a great photo.

Hi,

Checked the 1500uf and 1000uf electrolytics and they are HM(M) and KZG.

Some photos that have been taken (apologies they're not very good quality) are as follows:

http://img266.*************/img266/4932/image031x.jpg

http://img17.*************/img17/4896/image032lec.jpg

http://img17.*************/img17/5885/image033ekw.jpg

Best Regards.

**newbie2linux** · 05-12-2009, 05:22 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by PCBONEZ

You can get APL1084 spec sheet here.
http://www.anpec.com.tw/searchProduc...eyword=APL1084

Hi,

Thank you. At a guess the APL1084 is working properly as the 3.3v supply rail is the only supply rail that is working however no doubt it shouldn't be getting so warm. Is it worth recapping the 1500uf and 1000uf electrolytics in particular? is the replacement of these likely to cure the 'will not POST' problem and allow for the other power rails to operate as they should do?

Thank you.

**PCBONEZ** · 05-12-2009, 06:22 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Originally posted by newbie2linux

Hi,

Checked the 1500uf and 1000uf electrolytics and they are HM(M) and KZG.

Some photos that have been taken (apologies they're not very good quality) are as follows:

I've had a few boards go stone dead and KZG were the only problem.
They weren't bloated at all.

The HM usually bloat when they go but regardless if they are dated from 2001-2004 they should be replaced.
Date code is like: H0344.
The "03" is for year 2003 and the "44" is the week of that year.

**newbie2linux** · 05-27-2009, 05:20 PM

Re: VIA EPIA ML Mainboard no longer powers-up

Thank you to everyone who posted a reply. Shall try and recap this mainboard and hope that this will remedy the fault condition. Best Regards.

Announcement

VIA EPIA ML Mainboard no longer powers-up

VIA EPIA ML Mainboard no longer powers-up

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment