Spark & fry at battery transformer

[kjtruitt0]

I bought a used Dell d630 that didn't power up. Initially there was no voltage showing at the dc jack exposed metals. I read that I should be checking the underside, so I flipped the board over...still nothing. Prodded around, scraped a little bit of something off one of the plates on the back of the jack. More prodding. Plugged it in again and I got several sparks from the opposite end of the motherboard near the battery prongs.

I unplugged and instpected the underside and there was a dark area under some black plastic. Two solder rectangles had black charring between them. One of them distintegrated when probed with a screwdriver. I cleaned up that area, thinking that somehow there had been a short between these two solder rectangles.

On the top side of this section of the board there is one of three black objects within which wound copper wire can be seen. I'm assuming they are transformers for the battery usage or charging process.

Anway, after having cleaned the underside up and completely scraping away the remains of that one solder tower/rectangle, I plugged it in again.

No sparks, and now there is 19 volts at the plates on the reverse side of the dc jack.

I'm assuming that the battery will either no longer charge, or that the computer can no longer be run on battery power.

I cannot detect anything but old solder in this debris I scraped away. The location of the former solder tower appears to have pins on each end. Can I just build up some solder here, making sure not to connect to anything around it, and expect it all to work again?

 

[kjtruitt0]

I think this solder rectangle must have been a fuse. Anyone know where I can order a replacement fuse for a d630? And this doesn't mean that I simply blew a fuse so replace and all is well. I still hope to hear from someone with some insight into what's going on here.

 

[kjtruitt0]

I produce actual *sparks* from my motherboard and nobody cares to comment? What's it take?

 

[jarotech]

Don't be too cocky, you bought a defective laptop and expect someone to help you repair it. You have no clue what is defective about the laptop. If you take some pictures where you think you have the problem, that will be useful.

 

[kjtruitt0]

Don't be too cocky, you bought a defective laptop and expect someone to help you repair it. You have no clue what is defective about the laptop. If you take some pictures where you think you have the problem, that will be useful.

I have some pictures that I put up somewhere else since I can't see how to do it here:

mobo pics <--URL IS GOOD NOW

I am not sure whether that fuse was still good when the original problem of no power to unit manifested. I think it may have been. I only got sparks--and I think the fuse only blew--after prodding the dc jack a bit. So one possibility is that the jack has just become loose,and in the course of prodding it I revived the circuit, but unfortunately something was causing a short somewhere--possibly something from my kitchen table, although I think it was just on varnished wood, and the fuse blew at that time.

Thanks for your reply.

 

[jarotech]

Hi, I don't think what you are refering at, are fuses, generally fuses have a white body. On the last picture, you wrote, one good fuse next to a missing fuse, the good fuse has a light brown body, this is a capacitor.

 

[GUNNY1966]

I'm lost due to you stated in the pictures given/linked you scraped it anyways! What exactly are you asking?

 

[kjtruitt0]

OK so that's a capacitor. So I'm asking does anyone have a notion as to what happened here and what I can do to fix it. I "scraped it" because it had already cracked and a piece came off. So if I solder on a capacitor from an old t60 board that looks *exactly* the same, assuming I can do this, is this going to work? And also, why would a capacitor blow. Also, why would there initially be no voltage at the dc jack then after the sparks there IS voltage?

What is in the back of my mind is that I read that power goes straight from the dc jack to the battery stuff, which happens to be where the sparks were. Did I short something out by having it face down on the kitchen table somehow? or were the sparks due to the fact that the formally inoperative dc jack apparently got pressed into a position where it was functional, and then what may have been a pre-existing problem with the circuit reasserted itself and the capacitor blew.

That capacitor is right below the magnet-wound wire deal on the underside of the board. What happens if you blow a capacitor? If I somehow sealed it off so that it was not a danger to short anything else, would the motherboard function?

Really, anything you may know about this is probably something I don't know.

 

[kjtruitt0]

Ok I did in fact break off a capacitor from the T-60 board and I couldn't really solder it in place on the d630 board since I don't have any solder--so I used a tiny bit of fabric glue to stick it in place--approximately. Then I put it all back together (ripped out the modem because I crushed the plug while removing it) and ... booted it up to Linux.

Does anybody know what these capacitors look like uninstalled? Do they have pins on each side which are inserted into the motherboard, or are they just soldered in there?

 

[GUNNY1966]

Some have pins & some are manufactured with solider nipples so they can be removed & installed rather simply. As for the look of the capacitor, that means NOTHING as the RESISTANCE it supplies may differ. Finding the schematic for the board & finding the EXACT capacitor with the CORRECT resistance is the key to success via the resistance notation & key values given in the schematical diagram! FACT

 

[kjtruitt0]

Some have pins & some are manufactured with solider nipples so they can be removed & installed rather simply. As for the look of the capacitor, that means NOTHING as the RESISTANCE it supplies may differ. Finding the schematic for the board & finding the EXACT capacitor with the CORRECT resistance is the key to success via the resistance notation & key values given in the schematical diagram! FACT

I rather suspect that current is not actually passing through the capacitor I glued on there anyway. I think it has to do with charging the battery, or running on battery power, an that these operations wouldn't work. I'll check it out. But seems like there'd be a decent chance that the capacitor was the same spec--looks the same and pulled from another laptop motherboard of similar vintage--if the capacitor that looked the same was pulled from a boom box or something, I would not expect much chance of it working.

I'm going to pick up some solder and try to really get it on there. I think there were pins and the pins are still in the board, so soldering on top is going to have to do it. I'm also going to try a battery on before this. Anyone know what the current should be like at the battery interface contacts? I think there was hardly any voltage when I checked--2-3 volts if anything.

 

[GUNNY1966]

Did you look to see if the manufacture has a spec sheet posted?

 

[kjtruitt0]

Did you look to see if the manufacture has a spec sheet posted?

I've only seen them for $15, which is not in the spirit of this project.

I have looked around and found out that these are possibly 'decoupling capacitors'. In some discussions about whether to replace them people have suggested just letting them alone--saying things like Intel recommends 30 or more such components in a motherboard, and most motherboards have 50. This might explain why the board is working when I probably haven't really replaced the capacitor yet.

But I was mostly interested if anybody could provide a good theory as to what happened here that accounts for all the facts--no power initially, then sparks (maybe blowing the capacitor, maybe it was already blown partially?), then later power and successful operation.

-------------------------------------------------------------------------------------------------

I knew somebody who uses their d630 strictly at the desktop and swapped out the pc with that one. The laptop worked just wouldn't charge the battery, and no battery was needed here so that is fine. But you know it could be that the reason the battery wasn't being charged is that I was using a 65-watt adapter rather than a 90-watt adapter. This is a whole 'nother topic.

And finally, regarding those little brown things you see all over the motherboard--I think they may be inductors rather than capacitors, assuming there is a difference. In my limited understanding, inductors work to keep the voltage from spiking, while capacitors basically pick up the slack in the current.

Look for my new thread regarding no power in a d630 motherboard that suffered chocolate milk damage. Over and Out.