[DVE]

Hi all,

I am trying to repair the Indigo2 audio module, which had a burned tantalum capacitor.

This is how my board looks: https://i.postimg.cc/tCbNbqxF/image.png

If possible, can somebody make a high-res image of the board? I want to see the capacitor value and how the traces were connected.

Thanks

[weblacky]

Another user recently had a similar issue. Hopefully caps are the same (likely they are):

http://forums.irixnet.org/thread-3160.html

Also while there are users that will disagree with me, normally these tantelums are incredibly stable. The only time that they tend to be unstable is when they were exposed to more ripple current than they’re derated for.


So I would highly suspect your power supply is responsible for this. Then again there is the off chance that it literally was the cap and it’s just not meeting its specification anymore. But that’s my two cents.

[robespierre]

Also while there are users that will disagree with me, normally these tantelums are incredibly stable. The only time that they tend to be unstable is when they were exposed to more ripple current than they’re derated for.

Or reverse voltage, or voltage above rating, etc.

So I would highly suspect your power supply is responsible for this. Then again there is the off chance that it literally was the cap and it’s just not meeting its specification anymore. But that’s my two cents.

I had this happen on an Indigo2 that was less than 5 years old. So I think there is just a design flaw in the circuit.

[DVE]

Thanks for the link.

In my case the damage is more severe, the heat was strong and the PCB is slightly bent under the capacitor.
And what is worrying me, I've tested my board with a multimeter, and there is a 0 resistance between these points:



(I've used a photo from that thread as a reference)

It may be a short circuit inside the damaged layer, if somebody can check with a multimeter if there is a connection between marked points that would be helpful.

As for the caps in general, pity to say, but this case is not extremely rare, I've already repaired a Compaq Portable from 1984, which had a burned tantalum capacitor. Maybe their parameters are degrading within years, but the nasty thing is that when the tantalum is broken, it became a short, which may cause bigger damage. In my case, it looks this https://i.postimg.cc/htsBzNBy/image.png and I'm not 100% sure yet that it can be repaired, if there is a short circuit between the layers.

[weblacky]

If you're feeling really adventurous you could always try to grind away the bubbled-out area and see if you can eliminate the short and rebuild the plane and all that jazz. It may be possible but it may not be financially worth it.

The good news is this audio card is removable and another can be gotten. I used to see modules on eBay frequently (though supply offerings have changed and I don't see any right now). If I were you I would just contact what few USA SGI dealers remain and ask them for one of these cards. Then to hedge your bets you can always just buy new capacitors and put them on the replacement card before you start using it.

I'd still try to grind it just to see what's there. It is on the edge so it might just be clear of the tracks leading to some of the larger ICs nearby and if you go slow with something designed to do this you may find that not all the planes have been welded together and it's only the two adjoining planes.

[DVE]

Yes, I've tried to make a bit of "surgery" and to cut the damaged layer, it is doable to replace some traces but without having a schematic, service manual with a module pinout or at least, a working module as a reference, it's hard to tell if connections between points are real or unwanted. So, I will postpone it for now, maybe I'll find a spare module later. The closest shop to me is sgidepot.co.uk, where I saw an audio module for 25 UK Pounds, which is about 40$, I can buy it later there or maybe I'll find something second-hand on eBay.