Friday, June 15, 2012

Fixing a Dell Vostro 1000 Power Supply: part 2

A couple of weeks ago, I posted about fixing my son's laptop that stopped charging the battery and running off of the A/C adapter.  I had isolated it to one component on the motherboard that I thought was a capacitor and took off to find a schematic or at least the part value.

Turns out the part was actually a ferrite chip.  That makes the measurements I made pretty worthless when I was assuming it was a bad cap.  Anyway, thanks to a remarkably quick response from ghn on http://www.notebookforums.com/, I was able to find http://lqv77.com/downloads/  which had a schematic for the laptop.  From that I found that the part in question  (FL1) was a ferrite chip BLM41PG600SN1L.  I found it on Digikey.com at 0.54 for quantity 1.  Of course I bought 5 - they are cheap and worth having on hand for future designs and repairs.  Well, that and about another $50 worth of parts that I had on my wishlist for future projects.

I decided since it was not completely clear that the capacitor PC134 (.01uf 25v Ceramic in a 0402 package) wasn't a problem, so I replaced that also.

My hot air rework station came in handy for this.  I cleaned up the pads with some additional solder and flux to get it to flow, then removed the excess with desolder braid.  Soldering the ferrite chip (a 1806 package) was a piece of cake.  The capacitor - not so much.  The 0402 package is really small, making it ridiculously hard to hold it in place.  I really need to get some really good tweezers to work with parts that small, and maybe a syringe of good solder paste for reflow soldering.

After a bit of fumbling, I managed to get it tacked down, then used the hot air to reflow it.   I cleaned up the excess flux with some alcohol.

I connected the battery, and power switch board, then plugged in the power.  The charging light came on, which I counted as a success.

It took me an hour or so to carefully reassemble the laptop, which has worked perfectly ever since.

For details on the troubleshooting process, see my previous post

2 comments:

andrew fields said...

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Wanderer said...

Thank you, Vince. I ordered an used mother board and maybe didn't need it. I don't do a lot of electronics any longer, but as I'll have to remove the old mother board any way, guess I'll suit up for some diagnostics. Now, where'd I put my Fluke - lol.