diagnosing dc jack or motherboard

[tempusfugit]

My question is how do you guys diagnose a computer with no power whatsoever?

My general procedure,

-reseat memory
-remove battery and charger, hold power button for 20 seconds
-reseat keyboard

So now I'm pretty sure its DC Jack, Mobo, or a short in the mobo/another connection.

Next step, I test the battery terminals with it plugged in with a multimeter.. Most of the time if I don't get steady voltage I just call it a bad dc jack. most of the time I'm right. I know you can test at the back of the dc jack too, but I don't want to open laptops for an estimate.

Also, how do you check everything else if its not powering on? Obviously I could pull hard drives and check them in another computer with ubuntu, but then I get some with viruses, who don't want to pay for a dc jack AND a virus. Or customers that swear up and down the keyboard was working fine before they brought it in, and I end up replacing a keyboard for free.(or sound not working, touchpad, etc)

So in short, my two questions are

1)Is there a better methodology to diagnose a bad dc jack?
2)Is there any way to power up a laptop with a bad dc jack and no charged batteries available? I have visions of some sort of universal battery emulator/test bed that you could hook up to the battery terminals and set the voltage/amperage, but I'm thinking such a thing does not exist.

 

[MobileTechie]

No, I'd say you're doing as well as you can without taking it apart. You can only do so much.

 

[Slaters Kustum Machines]

One last thing I would try is remove the CMOS battery for 30 seconds if it's not soldered to the motherboard.

Now that I think about it I had an old Gateway 400sd4 that showed no signs of power and I left the battery out and unplugged overnight. I thought for sure it was the motherboard and was going to order one the next day. Next day comes and for s*** and grins I put the battery back in and plugged in the power adapter and it started right up. I scratched my head and assumed that there was residual power that needed fully drained. Maybe that will work maybe it won't. Only seen it work the one time and it was a fluke.

 

[phaZed]

It should also be noted that even on many "dead" systems the charging light still comes on.. of course if it does, then it's not a power issue.

 

[732914TECH]

if you put a multimeter to the battery terminals and get between 3-5 volts on some of the pins, id say the DC Jack is fine, does the charging light come on?

 

[tempusfugit]

if you put a multimeter to the battery terminals and get between 3-5 volts on some of the pins, id say the DC Jack is fine, does the charging light come on?

This isn't a specific case, but I'm asking about cases where the light does not come on at all.

And the 3-5 volts should be steady right?? I've had ones that get voltage right when I make contact but drops to 0. Making me think, well voltage is going through the dc jack obviously, but perhaps the board isn't regulating it correctly to the battery.

 

[PC-Man]

If there is no power at all. First you need to ask the customer how the problem started, have the customer ever had problem with the power plug? like placing the plug in a special angle to get it charging. Because DC problem cannot happen overnight, if the customer never had any problem with charging or tunning the power plug to get the laptop power on/charging then there is no need to suspect the DC Jack.

If the laptop turn on but no display:
Reseat memory
Connect to external monitor

If after following these 2 simple test and still no joy.

I will look into the Video chipset, and will reflow the onboard.

I have had 80 percent success with reflow.

 

[joydivision]

Another trick if powers up press the caps lock key, if the LED doesn't come on you know it isn't POSTING, if it does you know it has POSTED and the problem is with the display.