What is this laptop motherboard component?

GK, You can get the data sheet here.

-- Tony Marsillo Nutmeg Repair

Thanks Tony,

So the part number I should be looking for is "TPS2042A"? And is it fairly straight forward to solder? I'm by no means an expert. There's probably other undiscovered damage to the motherboard that I might have to worry about too...

Thanks again, gk

Texas Instruments logo. A wildcard search (*2042a*) at

turns up the TI TPS2042A, described as "0.7A, 2.7-5.5V Dual (1In/2Out) Hi-Side MOSFET, Fault Report, Act-Low Enable." The data sheet for that part, downloaded via the link provided, describes it as a "current-limited power distribution switch" and shows that it does come in an 8-pin package which resembles the one in your picture. So, I sorta figure that's what you have there. Must have made a nice BANG when the leg came off :-(

This is apparently an obsolete part - none of the usual distributors such as DigiKey or Mouser have any in stock, and (apparently) neither does TI.

TI lists it as having been superceded by an "exact replacement", the TPS2042B. Digi-Key has the TPS2042BDR in stock for $1.68 each.

That's likely your best bet, I think.

--
Dave Platt                                    AE6EO
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I _think_ that is right. If so, TI's page for it at

says it has been replaced by the TPS2042B. That page says it is basically a power switch that can handle up to 0.5 A, which is a relatively large current for inside a laptop. The fried pin looks like the the input voltage to the chip, and the one immediately to its left is ground. That looks like a good set-up for a short from the spilled water.

Digi-Key sells the TPS2042BDR for about $2 each.

?Ref=395069&Row=70309&Site=US For orders below about $25 I think there is an additional handling charge.

I haven't had much experience soldering surface-mount components. You need a soldering iron with a fine pointed tip, not big and stubby, and having some small-diameter solder also helps. If you've got an old junk network card or hard drive or something kicking around, you might practice unsoldering and resoldering components on that before attacking the laptop.

has good information on soldering and desoldering.

Matt Roberds

It's a Texas Inst. TPS2042A MOSFET fault report, act-low enable. DCFR=Dual Cmos Fault Report. Datasheet at

Actually I find a big stubby tip works well since I can load it up with solder. The trick is to tack solder a pin in one corner, or glue the chip down, then apply a little pool of liquid rosin flux over the pins and drag a blob of hot solder on the tip of the iron across the leads slowly, the effect will be much like the original wave soldering, might want to practice on some junk first though. If you make a solder bridge, some desoldering wick can clean it up, apply more flux and try again. When finished, wash off all the flux.

The correct method of removing the old chip is to get a pair of fine anti-shock diagonal cutters and cut the remaining legs off the chip at the package. You can then carefully unsolder the cut off legs from the motherboard, one at a time. Position the new chip with a bit of double sided sticky tape (or suitable substitute) and then carefully solder the 8 legs.

Attempting to unsolder all the remaining legs in one go (unless you have the correct tools) is asking to destroy the motherboard.

Not in that state. You're going to have to do some major track rebuilding. Not only that, if it's a 3 layer or more board, it might not work as it could've eaten through another layer and you've no hope in hell of tracing that.

Even if you do get it soldered, to do that much damage needs a hell of alot of current and there's probably damage to other components too.

--
Conor

"You're not married, you haven't got a girlfriend and you've never seen 
Star Trek? Good Lord!" - Patrick Stewart, Extras.

Highly likely something else has been killed too then if it's a MOSFET and there's that much damage.

--
Conor

"You're not married, you haven't got a girlfriend and you've never seen 
Star Trek? Good Lord!" - Patrick Stewart, Extras.

The pad is completely missing, leaving a thru-hole visible where the pad used to be. You'll have to trace that thru hole and see which component it leads to so you can link it with wire.

IMO, this is not a practical repair for anyone but the most experienced engineer. It's almost certain that when the component shorted it took out other semiconductors, possibly the regulator IC, chipset IC, maybe even the CPU.

Your best bet might be finding the same model with a cracked LCD on eBay, and swapping the LCDs over. However, even the same model laptops have been known to use different LCDs.

Dave

I would try just cleaning away the corrosion first. You might get lucky.

Mark Z.

You might want to take a closer look at the second picture ;-)

Dave

I'm afraid you are cooked! It looks like the pad for the part is gone also. If there was an electrical short afterwards which fused the metallization, it may have caused damage to the metallization runs underneath. At any rate, it may be impossible to make connection to that one pin unless you know exactly where it goes and can put in a jumper.

Al

On Wed, 30 Nov 2005 10:31:09 -0000, "Dave D" put finger to keyboard and composed:

I'd remove the IC and check the voltage on the input pad (after you've repaired it). I'd also check for shorts on the output pins (6 & 7). It may be that one of the IC's internal MOSFETs failed catastrophically.

-- Franc Zabkar

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