What are basic diagnostic tests on a Windows laptop that won't boot?

Those of you with experience troubleshooting a dead laptop, can you provide advice?

I have a Windows 7 HP G72 laptop which suddenly stopped working. Do you have an idea how to do basic troubleshooting?

What happens when I try to reboot is that nothing shows up on the 17-inch screen whatsoever.

The only indicators are the fan and a half dozen LEDs.

The fan is most notable. When I press the power switch, the fan goes on for what I timed at 40 seconds. Then the fan goes off.

The white LED to the immediate left of the topside power switch glows white when the computer is turned on.

The orange and white LED next to the power input on the right side of the pc also glows either orange or white.

The white capslock key LED blinks white synchronously with the NumLock key. The F12/WiFi function key glows orange.

The tiny LED on the DVD tray button does not light, nor will the DVD tray open unless I insert a paperclip.

I found this "maintenance guide" but it doesn't seem to list these conditions:

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Those of you with experience troubleshooting a dead laptop, can you provide advice?

Mainly I just want to know if I can pinpoint the failure and then I can see whether it's worth trying to fix.

Reply to
Calia
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Actually, now that I have said that, my second timer run shows the fan continually running.

So, to clarify, the only indications of anything working are the fan runs continually, and a few LEDs light, as stated prior.

Curiously, the hard disk drive LED light on the left side does not seem to be lighting up at any point.

Reply to
Calia

Does it have a door you can remove to get to the memory card? if so, remove the memory card, clean the contacts (gently) if they appear dirty, and re-insert. You might blow dirt out of the connector before putting the memory card back in.

Otherwise, some computers have various connectors between various components, and some of these can work loose with handling. There's always a connector for the LCD screen, but these are likely very hard for a non-expert to get into. You might also pull the hard drive and re-insert. Sometimes that will fix a problem, although you'd usually get a failure message when it can't read the hard drive.

Jon

Reply to
Jon Elson

Ugh!!! I take it it's not under warranty? Even with the hard disk toast I'd expect to see the display come alive. Has the power brick given up? That's about only test I can suggest, e.g. is it providing 12 volts or whatever. Try to find another rated more or less same and try it instead.

Other than that if it's not under warranty and you can't find some "specialty shop" deals with laptops almost exclusively you likely have some parts is about it, e.g. hard disk can likely be used in some enclosure as an external drive etc. Fact of the matter is cost of time to repair likely comes close to cost of replacing. Sorry for your loss.

Reply to
pjp

Calia wrote in news:llucdm$jre$ snipped-for-privacy@news.albasani.net:

Bad RAM will stop boot too.

Reply to
Geoff

The warranty died long ago.

Nothing shows up on the display. Here is a picture with the power on and the fan running:

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I don't know. I will try to get test leads into those tiny holes. It appears to be charging the battery and the battery appears to work, so, I've tested all three cases: a) With just the battery b) With the AC power and the battery in c) With the AC power and the battery out

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Reply to
Calia

It's a little tricky removing those memory cards. They seem to have a fancy "clasp" on the sides, but, I will keep trying until I get them out:

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I am taking your advice and have removed the hard drive, and will re-insert soon:

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Reply to
Calia

I removed the two memory cards, and swapped them, and put them back, and powered up, but to no avail.

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Reply to
Calia

I found this video which at least shows me how to disassemble the HP G72 B54NR to get at the CPU to see if it can be debugged:

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Reply to
Calia

You test the memory SODIMMs, one at a time.

Do not insert both.

Try only one of them.

If still a problem, remove that one and try the other. It is unlikely for them to both fail at the same time (although that has happened to me).

Paul

Reply to
Paul

Black screen with blinking error code LEDs are described here.

Try to match the table info, to your machine. Applies to UEFI BIOS machines.

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And this is my proof that a G72 may be using a UEFI BIOS.

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Paul

Reply to
Paul

I will likely try overheating the motherboard, to solve this problem, as per this video on the HP G72:

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Reply to
Calia

I get a single blink, which translates to: LEDs blink 1 time, CPU, CPU not functional

It seems the CPU disconnects from the motherboard due to solder cracks, at least if I understand Jeff correctly.

Reply to
Calia

Not necessarily true. It could be the VCore regulator near the CPU socket which is not functioning. It could be a loss of power feeding into the VCore regulator (like a problem with the circuit distributing power from battery to elsewhere inside the computer).

CPU/Processor chips are very reliable.

On laptops with a separate GPU chip, some of those have problems with cracked solder balls. But for the CPU socket, it could be using a thruhole socket with land grid array springs to make contact with the CPU. And that doesn't have nearly the same issues as a fine pitch BGA might.

Also, when you see LEDs blink, they may not be blinking due to the "test procedure". They could instead blink because of the way a power failure is happening inside the unit. For the entries in the table with multiple blinks, seeing the LED blink multiple times would be a reasonably reliable indication of a problem. But when you see one blink, is that a "CPU test failure", or is it "the power regulator just turned off". We don't know. Some test results will not be that accurate and specific. And it would be a mistake to jump to a conclusion just yet.

I would retest with battery pack IN versus battery pack OUT, and see if the timing of the blink changes at all. If if was a true CPU test failure, the timing should not change at all. If the blink duration seems quite different, between those two test cases, it could be an internal power distribution issue.

Paul

Reply to
Paul

If the overheating of the motherboard doesn't work, is it feasible to remove the motherboard and somehow, "reflow" the solder joints?

For example, in this video, a guy removes & replaces a chip with some sort of brass torch tool:

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Is the IC replacement as easy as that video makes it seem? (Seems to me the chances of getting all the pins lined up and nothing shorted elsewhere has got to be near zero.)

Reply to
Calia

You use a hot air rework station for BGA replacement.

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On good quality PCB material, a BGA site can be repaired up to three times, without damage to the PCB. Computer motherboards are not high quality, so your mileage may vary.

The hot air rework, applies heat from the top of the PCB. It also applies heat from the bottom. This is to reduce stress on the PCB. On the top side, the area to be heated, is controlled by fitting a metal "hood" to the nozzle. There are different sized hoods for different sized chips. (We had at least 20 different ones for our machine at work.)

On the top side, a "vacuum wand" can be used to lift the molten-hot chip off its PCB site. That's when it is hot enough. The small knob on top of the tool in the picture above, could be related to chip release.

When you put down a new chip, the soldering process is "self aligning". When the new chip is heated, to make the solder balls melt, the surface tension of the solder helps "attract" each contact, to its mate on the PCB. So even if the chip is rotated 1 degree from ideal position, it will "snap" into position when the solder melts. This reduces soldering defects to around

1 bad connection in 100,000 solder balls.

When a repair is finished, a 2.5D Xray machine can be used to verify the quality of the solder joints. Pictures are taken, using Xray energy, at an angle off the vertical axis. And any balls with a "popcorn" problem, can be seen in the picture taken with the Xray energy. I've never seen one of these in person, but our factory had one. Every large chip was verified with one of these (as part of closed loop process feedback). Eventually, once all the kinks are worked out of the manufacturing process, this might not be as necessary.

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A company in town used to do this repair here, but they charge $1000 per chip. They have this high charge, because their staff are mostly idle. And the company has likely long since closed up and moved. In Taiwan, where staff do this for a solid eight hours a day, the cost of repair is a lot lower.

Depending on the ball count, pitch, and so on, there may also be "underfill" materials squirted underneath the chip. This forms a solid which helps control stress when the product is at its normal operating temperature. I know nothing about how you deal with underfill, when such a chip needs a repair. Underfill would be a popular solution for stand-alone GPU chips. (I don't even know what materials to use, so this is just an illustration.)

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*******

Home computer repair people, they use the "oven method" to repair GPUs. Which is about as dumb and dangerous as it sounds. While the repair may seem to work at first, the track record of such repairs is not perfect. Temperature profile is completely uncontrolled - plastics may melt on items which were not intended for this sort of treatment. Proper repair with a hot air rework station is better, because the temperature profile is controlled during the entire operation. You can use the chip manufacturer recommended profile, when doing a repair.

Paul

Reply to
Paul

The timing of the single blink remains whether I use the battery or the AC power supply without the battery.

I am googling how to reflow the motherboard and it looks like I have three major options (none of which are really all that good).

  1. Cover all fan ports & run the PC hot for 20 minutes.
  2. Disassemble & reheat specific chips (e.g., cpu).
  3. Disassemble & bake motherboard in the kitchen oven.

None seem particularly safe.

Reply to
Calia

Here is the procedure I may need to follow:

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Reply to
Calia

Thanks.

It's not impossible to do SMT repairs, but it does help to have the right equipment and plenty of practice. Also, if you're replacing parts, it might be helpful to have a supply of known good replacements. Cannibalism from other motherboards works in desperation, but is not a good idea. I use a Chinese hot air SMT workstation that I bought cheap on eBay for about $80. Make sure you get a good selection of nozzles. The video you mentioned should have had some aluminum foil around the chip to prevent the hot air from melting nearby parts and plastic.

While this may be above your present abilities, I suspect that throwing money at the laptop is not going to work because it will probably cost as much as the laptop is worth to fix it. Big and awkward 17" laptops, with only 1600x900 displays and a slow CPU, are not exactly in demand. In the past, I've removed the motherboard, and sent it off to a random reballing service: It usually cost me about $150 plus about $20 shipping each way. Add 2 hrs of my labor to tear it down, and put it back together, and I'm well over the value of the machine.

It's unlikely to be the CPU. I haven't seen a dead Intel CPU for maybe 10 years, and only a few older AMD Athelon chips that blow up when the heat sink is dislodged. The CPU is in a socket so you can easily replace the CPU. Photos: The big white socket is for the CPU, which appears to be an Intel

2.0GHz P6100. Cheap. From your detailed description (thanks), it looks like 1 flash, which means "CPU not functional". More likely, it's one of the other chips holding down the address or data lines causing the CPU to misbehave. I can't tell from here which chip without poking my scope onto the address and data lines.

One thing you can do is buy|borrow|steal a hot air SMT workstation and get some practice on this machine. Well, practice on some old boards first to get a feel for how much heat is needed and for how long. However, don't try to remove the chip. Just slop on a mess of paste flux, and heat it until the solder reflows. Maybe push LIGHTLY on the chip to get it closer to the PCB. If the astronomical signs are in your favor, you might end up with a usable board. If not, you won't be any worse than you started, and maybe you can do better on the next motherboard. Or just use it as a cat warmer:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

The theory is that since the BGA chips use low temperature (bismuth) solder balls, it doesn't take much heat to reflow the solder. The reality is that without flux, the broken solder connections are unlikely to fuse together.

The CPU is in a socket. Buy a cheap replacement on eBay and try it.

That will melt all the plastic parts (i.e. connectors). Bad idea.

There's a 4th option. Send it to someone with the expertise and equipment. Just watch your costs very carefully.

Well, they're a step above the Xbox repairs that use a sterno can under the PCB to reflow the solder.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

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