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

Most likely an inverter failure. .

On Mon, 26 May 2014 05:51:12 +0000 (UTC), Calia wrote as underneath :

You cant' reflow a motherboard and get away with it, you can sometimes replace a single chip if you know exactly what your doing and exactly which chip is the problem. Many laptops dont have plugin processors, there is no chance of replacing a soldered-in one! Suggest you head for the bin with this one having taken the hard drive out and lifting off any files you need to keep. If you really want to pursue the problem, there is a diagnostic board you can get for not much money from China, which plugs into the parallel port (which has direct access to the BOIS boot) and can watch every step of any bootup, it remembers the 4 digit codes for every step in the sequence so you can step through and interpret exactly where the BOIS stops booting, cheap kit - but not for the faint hearted, check your laptop has a parallel port! See : eBay item number: 400514258135 C+

You have received a lot of useful information and suggestions, so what I am about to say may be for naught: I have two G72 laptops. One I bought new and experienced much the same type of problem as you are after the warranty ran out. Being that I am one who cannot accept a device is not repairable, I dug into trouble shooting and repairing my laptop. At first I opened it up and inspected the connections because the problem was intermittent. I would disassemble the computer, reassemble it, and it would work for a time. Then it would fail again. Without going into great detail of all the steps, the solution to fixing this computer was to re-solder the connections at the power switch board. There appears to be an opto isolator on a daughter board where the switch is mounted. It takes a steady hand and a low wattage iron, but this computer has not failed in a couple of years since I touched up the connections. I think I fixed it.

After having fixed the above computer, I purchased another G72 computer on Ebay where the seller was encountering the same failure as mine. I bought it for little, and thought I would use it for parts if my computer ever failed. When I received it, it DID NOT include an AC adapter. I plugged in my adapter to the computer and everything worked!! That has been over a year now.

So what can one learn from the above? First off there appears to be some experiencing such failures that are attributed to the power switch board. There are such posts on the web. Second, if the adapter delivers less than the proper level of voltage to the computer, it too will fail in a similar manner. Measuring the voltage with a volt meter is not going to work unless you load it down sufficiently. If it were my computer, I would borrow a power adapter that you know works on that model computer. If it does not solve the problem, suspect the power switch board.

There are no guarantees as to what will solve your problem, and the fan running seems to contradict my experience, but a lot is happening when you start a computer. Any of them failing will negate the boot process. Good luck.

Just because I could, I tried booting to Knoppix, but it didn't even get to the BIOS screen, which, if the CPU is reporting itself bad, would be the case.

I don't think Windows 7 would fare any better, but, I don't have a Windows 7 boot disk anyway.

I've read all the other advice, all of it good if you're comfortable messing with hardware, etc.

However, your _first_ concern should be to get all your data off the disk drive, and that can, and IMO should, be done without repairing the machine. IMO best bet is to take the machine to a shop that can deal with it. Then you can decide whether repair (by yourself or the shop) is feasible.

HTH & Good Luck,

Before you have disassembled anything, shine a flashlight (electric torch) at the screen, and watch closely as you power up. Maybe just the backlight has failed.

This is good advice, as had been all the prior advice.

I am heading down to Radio Shack today, if they're open, to pick up an SATA/ATA USB adapter, which will make it very easy to get all the data off the hard disk drive.

I've done that step before, and, even better, I recently made a backup of my data hierarchy only about a month ago, so there really isn't much data that I need to back up incrementally anyway.

I tried that, and saw nothing. Even in the dark.

I think the single blink of the numlock and capslock indicating a bad CPU (or the power to it) is the issue.

Most people here seem to indicate that the CPU itself didn't fry, but, that the solder joints honeycombed, and eventually cracked.

At least that's what I seem to have gotten so far out of the conversation.

The manufacturer's site may have some info on what you "see" and "hear" depending on what's wrong. Least used to be "x" beeps meant this and "y" beeps meant that type idea, maybe lights do similar?

Internal power supply likely provides a number of leads with varying power. Could be it's failed on one or more of them but not all hence see leds lit on some keys?

Again an experienced shop would know how to test all that, I don't. I also don't really like taking laptops apart IF I also have to put it back together and have it run :) I solder with a blowtorch LOL

That probably will work, especially since the drive is not failing and there's little risk of losing anything on it.

In the future, you might consider doing an image backup instead. I use Acronis True Image 2014, but there are free drive cloning programs that will also work: Some of the benefits of image backups are:

- Speed. I just did an SSD to USB 3.0 backup running at 6 GBytes/minute. Typcial for older machines and USB 2.0 is 1-2 GBytes/minute backup.

- It backups up literally everything. Nothing is missed. That's great for programs the dump files in unusual places or strange stuff in hidden partitions. Also works with UEFI boot.

- In this case, it will also get the recovery partition, which you might need for a reinstall. The alternative is to order the recovery DVD's from HP (about $30).

- etc...

I'm at the point that everything that is brought to the shop usually gets backed up twice; once on arrival and once when it's done. That's about 6TB of drives show. There is probably another 5TB of drives that I've since the picture was taken. What makes this practical is the speed of the backup (and restore).

If you're near a computer-supply store, you might want to look for Vantec. I can recommend them from personal experience.

Yes and no; it takes practice!

Step by step through that video:

melting the solder on the pins of the IC with a hot air blower. Personally, I'd have some Kapton tape (like the yellow tape visible near the top of the video around just after 7 minutes in) over the other small components around: not so much as to keep them in place - if they're decoupling capacitors, it _might_ not matter too much if they're lost - as to stop them going off and shorting something else. It's easy not to detect these almost microscopic components.

Removing the IC. I'm pretty certain there was a skip in the video, as it seems to disappear by magic - one moment it's there, the next it isn't. The most important thing is to make sure all the solder is really melted: if it isn't at just one or two pins, you can pull off tracks (which are the devil to repair) when you pull the IC off. Ideally it will just blow away.

Cleaning up the solder pads. That's what he's doing with the solder braid (the copper woven strip) and soldering iron. Basically, you want to clean the pads until they're flat, no solder (other than a very thin flat layer).

Applying solder and replacement chip. It looks like he applied solder and then reheated it all with the hot air again. I'm sure that can be made to work; the way I usually do it is manually tack two opposing legs to hold the chip in place, then go around chasing a blob of solder around the remaining legs: amazingly, this does work, if the solder-resist is in reasonably condition. Lining the chip up before tacking is the difficult bit - doable, just takes patience (and a second or third try if it moves during the tacking: you just have to groan and do it, don't go ahead and assume you can fix it after you've soldered _all_ the legs).

The second half of the video seems to be replacing a surface-mount connector, by much the same means, though I think he does use tacking this time.

I'd agree with those expressing doubt as to whether it's worth it, and try with an external monitor first.

(Also, my own - extremely limited! - experience of laptop repair has been that cracks - in the solder joints or the PCB tracks around them - in the vicinity of the power input connector can be the problem: and lights can still come on, just there isn't enough power getting through to do anything else. If it gets to a dismantling and possible soldering activity, I'd reflow the solder around those before anything else: a lot easier than the finer chips. My experience replacing chips is genuine [avionics], but not with laptops. And I wouldn't expect to be able to reflow a ball-grid array.)

This model? $27 from NewEgg. Ouch. Note that I'm buying USB 3.0 these days because it's becoming common and the speed improvement is worthwhile.

Cheaper on eBay:

I was wondering what that was, as he seemed too close for it to be a flame burner.

I had never heard of this "kapton" tape!

Googling, I'm still not sure what it is, but it must be a great insulator.

I hadn't even thought of that!

It's a great idea.

I have one at work, which I can test out tomorrow!

Thanks!

My heavens! Stephen Foster wrote a song about it in the 19th century -- "De Kapton Races"!

"Oh, de Kapton ladies sing dis song -- Doo-dah, doo-dah. De Kapton racetrack five miles long -- Oh, de doo-dah day."

Kapton has been used to make orthodynamic loudspeakers. It's also used to cover waveguide ports, so the nitrogen within won't get without. (The waveguides are filled with dry nitrogen to keep moisture out.)

It's generally a thing not unlike a very specialised (usually with a temperature control) hair-dryer. You can get assorted nozzles, some shaped to suit devices; the one I think he was using was just the one that reduces the nozzle diameter to about a third, which gives a more directable stream (but you have to move it about more).

I think a flame burner would pollute the environment (I mean the board and components, not the planet) too much: you really need a fairly clean environment for fine solder, flux, and solder-resist all to work as they're supposed to.

I must admit I was just using the name those who taught me PCB rework used, though I _think_ it's correct. (The Wiki article doesn't mention this specific use.) Though not perfect - the adhesive tends to weaken a little under the great heat (and fair amount of wind!) required when removing a largish chip - it does a pretty good job of protecting (somewhat) the solder holding down the smaller adjacent components, and/or holding those components in place if their holding solder _does_ get melted. The fact that it's transparent helps too: foil, as mentioned by someone else in this thread, probably protects better, but you can't see through it.

As we use it, it's on rolls, looking like thin brown "Sellotape" (UK - Scotch tape I think US). I think the rolls shown in the Wiki article are like it (though not sure if those ones have adhesive backing).