VOGONS

My ASUS PVI-486SP3 blew up

Topic actions

First post, by Tetrium

Posted on 
User metadata
Rank l33t++
Rank
l33t++

Or atleast a part of it.

This is what happened:
I was going to test this board (I couldn't remember if I already had done so) to make sure it was (still) in working condition.
It had a DX2 overdrive in it and since it was already jumpered for the Intel DX (I usually test with a known-to-work AMD DX-40) I figured I'd just pick some random Intel DX-33 from out the parts box

Some history about the board:
I found it years ago while dumpsterdiving. It was in some oem desktop (cant remember the make) and it had that same overdrive in it. Hence it's quite possible that, since it was still installed when I went to test it, I never tested it before). The system it was in looked perfectly fine, no burn marks or smell or anything that would indicate it was defective back then.

So back to the story!
I double and triple checked the jumpers and the orientation of the cpu, installed basic working parts (ram and pci card), installed my standard AT test PSU and plugged in all the cables and plugged in all power cords.
It was laying on a cardboard box without anything on or under the board that could cause a short.
I was ready to boot the system!

I had my fingers on the power switch...

I switched the power switch and immediately after the power came on, heard a loud "BANG!", like a small fire cracker and I saw something small and glowing flying up in the air!
I thought the PSU had short circuited or something!
I didn't dare touch the PSU (for fear of being electrocuted, safety first!) and made a dash to pull the power cord from the wall!
The lights were still on, so it didn't short anything in the house.
With a flashlight I inspected the PSU switch which looked ok. I could smell a lil burn something, inspected the motherboard and noticed one of those small yellow balloons right under the power connector had blown up!

Ofcourse that PSU has been decommissioned.
I had been testing a couple DEC motherboards with it which wouldn't boot.
Perhaps that damaged the PSU somehow? I don't know for sure, I haven't opened that PSU yet to check the insides.

Looking at the yellow balloon it appears to be somekind of resistor.
The traces seem to go to around the BIOS chip area. Perhaps it was jumpered the wrong way?

I took some photos of this little disaster, perhaps someone here sees something I overlooked.

I'm hoping the board can still be repaired! Right now the board went back to it's cardboard box.

Here are the pics:

Pic1:The motherboard itself
DSC00340.jpg

pic2:the exploded 'yellow balloon' in the middle
DSC00338.jpg

pic3: (bad) photo of the markings on one of those other 'yellow balloons'
DSC00339.jpg

The board itself is a rev 1.22 one. I think one of you guys also had this exact revision of the board.

Any help is greatly appreciated!

Reply 1 of 7, by retro games 100

Posted on 
User metadata
Rank l33t
Rank
l33t
Tetrium wrote:

The board itself is a rev 1.22 one. I think one of you guys also had this exact revision of the board.

I can confirm that I have a 1.22 board, and I posted some messages about it here on Vogons, but unfortunately I couldn't get it to POST. I'm sorry to hear about your exploding 1.22 mobo! Hopefully it can be fixed somehow. I've often wondered what those yellow things are, and if it's possible to desolder a defective one, and to solder in a replacement. I've come across 486 mobos with those yellow things, and the tops of them are a black colour, as if they are beginning to degrade in some way.

Reply 2 of 7, by h-a-l-9000

Posted on 
User metadata
Rank DOSBox Author
Rank
DOSBox Author

The 'yellow baloon' is a tantalum capacitor. These, when growing old, have a habit of exploding like that. It's rather unlikely that something else was damaged from the incident so remove the remains of the capacitor and try again. It's not a critical part.

1+1=10

Reply 3 of 7, by 5u3

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

I agree. The board is most likely still OK. Just check the output voltages of the PSU before you re-connect it. Wikipedia has the pinout of the AT power connector.

Reply 4 of 7, by Tetrium

Posted on 
User metadata
Rank l33t++
Rank
l33t++
h-a-l-9000 wrote:

The 'yellow baloon' is a tantalum capacitor. These, when growing old, have a habit of exploding like that. It's rather unlikely that something else was damaged from the incident so remove the remains of the capacitor and try again. It's not a critical part.

Thanks, I was hoping it was old age. Of all the options this was the best one.
Wouldn't I still need to bridge the 2 solder points of the exploded capacitor?
I'm hopeless with the soldering iron (shaky hands), removing the old part, I might be able to pull off. I was considering bridging the 2 solder points with some silver paint *on the backside of the PCB) with a piece of tape between the solder dots. That way it would be very easy to remove the bridge made by the silverpaint, if it doesn't work.

Edit:I happen to have received 5 of those ATX 2 AT converters. From now on I'll be doing all my testing using a proven ATX PSU, just to be safe.

Edit2:

retro games 100 wrote:
Tetrium wrote:

The board itself is a rev 1.22 one. I think one of you guys also had this exact revision of the board.

I can confirm that I have a 1.22 board, and I posted some messages about it here on Vogons, but unfortunately I couldn't get it to POST.....

Yup, I know.
I tried really hard to come up with a solution that would bring your board back to life again.
Sucks having a board come in which turns out to be DOA, especially one of these 🙁

Reply 5 of 7, by h-a-l-9000

Posted on 
User metadata
Rank DOSBox Author
Rank
DOSBox Author

Wouldn't I still need to bridge the 2 solder points of the exploded capacitor?

Never!

1+1=10

Reply 6 of 7, by Tetrium

Posted on 
User metadata
Rank l33t++
Rank
l33t++

Ok, so I don't bridge the 2 solder spots with conductive mats.

Dunno if it matters, but after that thing exploded I didn't see any post screen. Must I remove it before I try again?

Reply 7 of 7, by ux-3

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

A capacitor is basically an open circuit for low frequencies. If you short circuit it, it will surely cause some damage. You could replace it:
Crumble off the remains and solder on another one to the remaining legs. Like 3.3 microfarad, check the others. Probably 16V or better. Obey the polarity.

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window