Laptop motherboard fixes with pressure

Mac PowerBook G4 won't boot (but will give the boot "bong"). If I press on the case below the motherboard, it boots and, if pressure is maintained, functions normally.

If pressure is released, video will scramble, and -- sometimes -- system will freeze.

I've run the mboard out of the case with just power, and pressed, squeezed,etc. without any hint of what I'm looking for. I've examined it with a glass looking for cracked board and/or traces, separating solder joints, the obvious. It does still fail out of the case, so this isn't a short-to-case issue.

Any ideas what else this might be? Do ASICS and other ICs fail (internally) in this mode?

Thanks,

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DaveC
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Remember that any modern computer motherboard is going to have a bare minimum of four layers. Most have six, and I've even heard of a few that have eight or ten.

It sounds to me like the board you're working with may have developed a hairline crack somewhere. Short of inspection with high-end ultrasonic or X-ray equipment (which probably costs more than you, me, and my wife make together in a year), I really doubt you're going to find the problem, much less be able to fix it.

Time for a replacement motherboard.

Happy hunting.

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Dr. Anton T. Squeegee

will

with

(internally)

It's gotta be a trace, solder joint, or via. Try resoldering anything in the area, if that doesn't work and it's otherwise garbage, you could try heating up that area of the board with a heat gun until it's hot enough to melt solder then let it cool off.

Reply to
James Sweet

It's probably a bad solder connection, but as others have said, it could be a crack in the board. I've seen a number of laptops with bad soldering on the DIMM sockets. Try resoldering everything that's easy to resolder with the equipment you have. On a board like that, there won't be much that's easy to resolder.

If the problem is on a BGA IC, you're out of luck. I guess you could try putting the whole board in an oven hot enough to melt all the solder. It sounds crazy, but that's how it was originally soldered at the factory. Andy Cuffe

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Andy Cuffe

On Thu, 26 May 2005 21:05:36 -0700, Andy Cuffe wrote (in article ):

I presume that components are physically attached to the PCB with high-temp adhesive before soldering. I'm concerned about components on the underside of the PCB falling off when the solder goes liquid.

If that's not an issue, I'm ready to try it. If I destroy the PCB, I'm not any further behind; I need a new motherboard anyway...

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DaveC

Appropriate temperature for this experiment would be 375F? (Google says melting point of 60/40 is 356.)

Leave it in for 10 min? 20?

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DaveC

You're probably better off with a heat gun so you can localize it, if you just put it in the oven the parts will fall off the bottom.

Reply to
James Sweet

On Sat, 28 May 2005 00:15:59 -0700, James Sweet wrote (in article ):

So how do they stay on for the original wave soldering? That is done with the PCB face-down, I believe.

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DaveC

you

the

They're glued on, so you might have some luck, but I've salvaged components by heating them until they fell off, so maybe if you don't go quite as hot the glue won't melt.

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James Sweet

The components are glued on, but it's possible that some of the glue has cracked with age and parts could fall off. The surface tension of the solder should hold the small parts on, but heavy parts could fall off if the glue has cracked. Put it in the oven with the large parts on top.

In the factory, they silk screen a solder and flux paste onto the solder pads, then glue the components on. Finally, it's pulled through an oven using a conveyer belt. It's important for the board to get hot enough to melt all the solder, but not hot enough, or long enough, to damage any of the components. I'm not sure if you could get even enough heat in a kitchen oven. I have no idea what temperature you should use, or for how long.

As others have said, a heat gun might be better if you can narrow down where the problem is.

What ever you decide to try, I would get a junk board to practice on. A few seconds too long with the heat gun could burn the board.

Let us know if it works. I've never tried anything like this. Andy Cuffe

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Andy Cuffe

Dave, as a suggestion perahps you could try the Mac groups etc to see if you can find someone with a similar unit, but crook or broken screen - might be a cheap way to solve the problem.

Another idea would be to talk to a Mac technician - he may know any common troublespots on your model board

David - who hates to see a good Mac go down

DaveC wrote:

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quietguy

I've done things like this a few times, and the technique that I found that seemed to work best was to position the board just above (1-2") a hot plate, and set the hot plate to just below the solder melting point. Then I could go into the board with a heat gun or soldering iron, depending on the task, and apply the small amount of additional local heat that the job required.

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Jim Adney

you can

cheap

Hah! A Mac technician? I remember those guys back when I was in highschool and the labs were filled with Macs. They'd come in and start swapping boards without doing any sort of troubleshooting at all. I'm sure there's some hardcore guys out there who attempt component level work but I've never encountered one.

The idea of finding another one with a busted screen is a good one, ebay is good for that too.

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James Sweet

On Sun, 29 May 2005 18:14:33 -0700, quietguy wrote (in article ):

can

That's the backup solution. I've got nothing to lose by trying the heat solution first.

Already have, several. They all say "replace the motherboard". Nothing against them; they've learned the modular-replacement method. I'm looking a little closer than that.

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DaveC

On Sun, 29 May 2005 19:44:19 -0700, Jim Adney wrote (in article ):

Thanks, Jim. This sounds like a good approach.

It brings up a couple of questions: how can I be sure that I don't exceed the pre-heating temperature (with the hot plate)? I don't want components dropping off of the underside of the board. And once I start to heat the topside of the board with the gun, how can I be sure I don't exceed the melting point of the solder? I understand that getting things too hot will melt the solder connections within an IC (they use a higher melting point solder to avoid this problem during manufacture of the PCB, or so I hear.)

Thanks,

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You may have to work up on the hot plate temp. The trick is to use it to heat the under side of the board to just below the melting point, so that the extra heat from your iron or heat gun will be enough to melt the parts you're interested in.

I don't think there is any solder in IC connections. The connections there are spot welded. The temp concern with ICs is that high temps will cause the doping ions to migrate and this migration may ruin the careful construction of the IC. This will be a time*temp thing, so you need to work as fast as you can.

ICs and transistors may have the silicon die soldered to a metal base, but I'll bet that this solder will be somewhat higher temp than where you need to work, but that's why you need to be careful not to heat any hotter than necessary.

Yes, it sure seems touchy, but I've managed to succeed a couple of times, with no failures so far.

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Jim Adney

"DaveC" bravely wrote to "All" (30 May 05 12:33:01) --- on the heady topic of "Re: Laptop motherboard fixes with pressure"

Da> From: DaveC Da> Xref: aeinews comp.sys.mac.hardware.misc:9529 Da> sci.electronics.repair:49238 Da> On Sun, 29 May 2005 18:14:33 -0700, quietguy wrote Da> (in article Da> ): > ... Da> as a suggestion perahps you could try the Mac groups etc to see if you can > find someone with a similar unit, but crook or broken screen - might be a > cheap way to solve the problem.

Da> That's the backup solution. I've got nothing to lose by trying the Da> heat solution first.

Da> Already have, several. They all say "replace the motherboard". Nothing Da> against them; they've learned the modular-replacement method. I'm Da> looking a little closer than that.

Dave,

They are not too far off the mark actually because a modern pc motherboard is a rather sophisticated piece of technology. To be fair, I'm assuming you have little repair experience and even less equipment than is available in a well equiped kitchen. Put it this way, it is as if you were to attempt brain surgery with stone knives and suture the wound using bone needles. Please, forgive me if my assumption is wrong.

A*s*i*m*o*v

... Back when I was a boy, we carved our own ICs out of wood.

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Asimov

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**THE-RFI-EMI-GUY**

On Mon, 30 May 2005 21:32:37 -0700, THE-RFI-EMI-GUY** wrote (in article ):

Thanks, REG. I did that. Yes, it's best to look for the obvious *one* failure rather than attack the whole board, but I'm down to that choice, now: heat it and hopefully fix it, or pay for a replacement board.

Nothin' to lose, right?

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On Mon, 30 May 2005 20:28:22 -0700, Asimov wrote (in article ):

Yes, all suggestions are correct: Replace with working MB: $$ Have repair shop repair the MB: $ Attempt re-flow of solder: $0

Will approach all repair procedures in reverse order (cheapest first).

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