Identifying hiding bad caps on motherboard

[themdg]

Hi everyone. A few weeks ago I came home to a strong acidic/electric smell in my home office. My HP XW6200 was still running, but the smell was strong. With my nose, I determined that it was probably something in the power supply, which I replaced. The smell is less now, but a variation of it is still there, and the machine shuts off after 10 or 15 minutes of use. (I tried it a few times, and have not had it running since.) Assuming the power supply was bad, I guess it could have taken out other components at it's demise.

I took the motherboard out and had a close look at all the caps. I don't see any that are bulging or leaking. I'm not sure where to go from here. Without physical evidence of a problematic capacitor, do I assume it's something else on the MB that's broken? Or can I power it back up and test all the caps with my multi-tester somehow?

I've replaced caps on a few bad LCD monitors successfully, but never did any actual cap testing etc.

Does anyone have any advise for my flagging xw6200?

[PCBONEZ]

Re: Identifying hiding bad caps on motherboard

Look for,,,
Nichicon HM or HN series [defective from 2001-2004]
.. and/or Chemicon KZG or KZJ series [known to fail with no bloating]
.. and of course crap brands.

Did you look under the heatsinks for hidden caps?
I know some have solid poly there but maybe not all do.

Check for burned pins in mobo to PSU power connectors.
[Both on mobo and cable.]

.

[Half-Saint]

Re: Identifying hiding bad caps on motherboard

Thanks for the tip. I was just about to post a question about fixing motherboards with no visibly bad caps. I think all of the ones I checked have Nichion caps! Got 13 broken boards recently that need fixing if possible...

Cheers

[themdg]

Re: Identifying hiding bad caps on motherboard

Thanks PCBONEZ. After some more pressing stuff, I'm back to searching this board. I've been going over it for a few hours with a flashlight and magnifying glass. So far, I see one thing that _may_ be suspect. I'll try to get a photo of it if I can.

All of the plainly visible caps on the board look ok so far. Most have either 3 lines on top, like a Mercedes symbol, or 3 lines that look like a K.

Forgive my ignorance here...but there are also a bunch of little dudes on there, and I'm sure sure what they are. About the size of small caps, but silver and cuplike. That is...one open end where the pins are, and one solid piece of silver metal (I guess). They have blue printing on the top, that reads "A54 595 60 V". There are larger and smaller ones with other printing, but the bulk of them are these A54 ones. What are these?

The reason I ask is that one of them is suspect. The is a nice zigzag row of them between the two processors on this board. One of them has a bit of grayish dust that seems to have come out from underneath it (stuck to the board, but easy to wipe off). I'm wondering if it failed, and this substance leaked out and dried. It's about the same color as the heat sync goo on the processors...so perhaps it's that. But it really does look like it's under the little cylinder.

What do you think?

I'll go over the board again from another angle...looking under syncs and at the pins really closely....see what else I can find.

[themdg]

Re: Identifying hiding bad caps on motherboard

...They have blue printing on the top, that reads "A54 595 60 V". There are larger and smaller ones with other printing, but the bulk of them are these A54 ones. ...

Upon closer inspection, I see now that the printing is actually
A 595
560
4 V

I was reading some things vertically that should have been horizontal.

Is that a 560 micro farad, 4 Volt capacitor? Would such a cap have something leaking out like this?

[PCBONEZ]

Re: Identifying hiding bad caps on motherboard

Three legit brands I know of use a K vent and maybe 500 use a Y vent.
Need logos or markings to go anywhere with that.

The other sounds like a Chemicon Polymer.
Series PSA -

Residue may be leakage or may just be flux Residue left over from manufacturing.

.

[themdg]

Re: Identifying hiding bad caps on motherboard

Thanks again PCBONEZ. They definitely were Chemical Polymers.

I found some posts on this board about different K and Y markings. Looks like most of my caps are Sanyo brand.

I took some photos. Tried to get a wide aperture and good light in case anyone wanted to see up close.

This is the residue I'm talking about:



That is about 1/4 of the residue that was there. Before I wiped it with my finger, it was a larger area...down to the white line. Is that the flux?

A few other photos of the board.










And loads more here: http://themdg.org/pics/posts/Motherboard/

[PCBONEZ]

Re: Identifying hiding bad caps on motherboard

The residue looks like it's just dust from the CPU fan.
The nearby caps are Chemicon PSA series Solid Polymer. [They only put the A on PSA's]
The Purple sleeved ones are Sanyo OS-CON Solid Polymer.

The Green w/K are Sanyo. Most likely WG series.
The Black one w/K is Rubycon [Note different style K.]

The Brown ones are Chemicon [note shield logo]
- Those I can see are KZE series.
Only Chemicon KZG and KZJ have issues. KZE is fine.
KZG have the same Brown/White as those KZE. [KZE are sometimes Green.]
KZJ are Black/Gold if I remember right.

Unless some of those Chemicon I can't see are KZG then caps probably aren't an issue at all for you.
.

[Per Hansson]

Re: Identifying hiding bad caps on motherboard

Hmm, Canon 5D, nice camera
Nice board aswell
I can't see anything wrong with the caps or board itself, of course caps can fail without sign, but it is unlikely when the board is this well designed...

You mention you had a PSU with something go bad, then you replaced the PSU
What replacement PSU did you use?
A brand new one or a used PSU? Maybe the new PSU is faulty too?

[themdg]

Re: Identifying hiding bad caps on motherboard

Thanks, Per. I shoot action photography on the weekends. Fun to have good equipment around. Someday I'll learn how to properly use it.

Too bad it's not likely one of my capacitors. I'll strip the box down to bare essentials, and do some burn in tests. Maybe do some voltage tests on the power supply.

Thanks for looking at my board. If I find the problem with the box I'll post it here in case anyone is interested.

This forum is a real asset. Someone gave me a almost-new 37" tv that was broke. $3 in capacitors later, good as new! I'm learning a bunch from these posts.

[themdg]

Re: Identifying hiding bad caps on motherboard

One more jab at this one... I thought for sure the computer was running too hot... the thermal grease on the 2 processors had not been replaced, and was pretty thick and splotchy. I clean it off and replaced it. Still shuts down whenever it wants.

Something is still up, becuase there is still a strong acrid smell (strong, the longer it runs). Maybe I'll take the new power supply back to the shop where I bought it and have them test it.

[PCBONEZ]

Re: Identifying hiding bad caps on motherboard

In the second picture the fan header pins appear to be shorted together.
Sorry I didn't notice earlier.
.