Laptop Motherboard Repair

[severach]

Re: Laptop Motherboard Repair

Wall warts are no good for short testing. 1A might be enough to burn the short out. Any more than 1A and the supply will shut down.

A bench supply won't shut down and allows you to control the current so you can get the shorted component to heat up without burning it up. Meters are good too so you know about how much heat you're looking for.

[spleenharvester]

Re: Laptop Motherboard Repair

Guys, would a 5v 1A wall wart that's been chopped up be good for "heat testing" for shorts?

Also anyone got any guides as to where to start? How to test FETs, ceramic caps, readings you'd expect to see on an ohmeter etc?

Cheers

[oxonater]

Re: Laptop Motherboard Repair

Hi I was wondering if anyone knows about this issue I have with the following laptop.

Toshiba Satellite P200-1EE
Model no:PSPB6E-0GMO28EN
K000057590

The LCD is blank and only get a mere white flicker stays blank as laptop continues its boot up process. I have changed the Inverter and no joy, I have a working backlight out of a smashed screen and when connected into a tested Inverter it doesn't light up at all. The laptop will work fine when connected to an external display. Have been told that this issue relates to a faulty power fet that supplys power to lcd circuit.
Any help would be great thanks

[bazzbarro]

Re: Laptop Motherboard Repair

u cant see anything even the dell logo this black screen just pop up

[sasser]

Re: Laptop Motherboard Repair

U see the bios setting before this error? Try to flash new bios

[bazzbarro]

Re: Laptop Motherboard Repair

sorry for my broken English i will try to cultivate it the model is satellite A100
about the images am unable to get them right away because its for client and i had returned it back before i get the tips and how to get started working on it i have good background on electronics so before i get the images where to begin

[bazzbarro]

Re: Laptop Motherboard Repair

dell latitude d610 gives this error i would kindly like to know which component on the m b can be repaired have tried all the basic tips on forum fn x bios settings test all memory's etc

****manufacturing mode :[67]****
press fn-x to return the system to normal running mode

[bazzbarro]

Re: Laptop Motherboard Repair

dell latitude d610 gives this error i would kindly like to know which component on the m b can be repaired have tried all the basic tips on forum fn x bios settings test all memory's etc

****manufacturing mode :[67]****
press fn-x to return the system to normal running mode

[bazzbarro]

Re: Laptop Motherboard Repair

dell latitude d610 gives this erro
****manufacturing mode :[67]****
press fn-x to return the system to normal running mode

[lord]

Re: Laptop Motherboard Repair

Hi bazzbarro!
First please use . and , because they are essentials to good communication.
Secondly you have to specify model of the laptop in order somebody can help you. It is also good to put the pictures of disassembled motherboard so we can understand each other better.
Regards to Kenya!
Darko

[bazzbarro]

Re: Laptop Motherboard Repair

hi have Toshiba satellite not powering on the led would blink a little when power supply first inserted or battery but would fade out kindly inform on the primary power testing points tips

[momaka]

Re: Laptop Motherboard Repair

What you need is a low-voltage, high-current source, preferably sub 3V and able to supply at least a few amps.

Probably what you want to do is find the part\branch of the circuit where you have found the short, verify there is in fact not supposed to be a short, and apply power there, and see what happens.

Correct.

However, be cautious with this method. CPU, GPU, and Northbridge power rails will more often than not appear shorted or with very low resistance. This is actually normal in most cases. Applying power on those rails with too high of a voltage can damage the CPU, GPU, or Northbridge.

Can anyone give a brief explination of how to use a bench supply to "smoke" out the shorted componant ? i know its probably not good practice but i have a couple of boards that i have extensively tested with my meter but have been unable to find the shorted part

The problem you have with those boards may not necessarily be shorted components. It could also be a bad connection, bad GPU or Northbridge BGA joint, open resistor (good luck finding that!), bad ICs, or an internally bad trace. In any of the above cases, a bench power supply won't help you much, other than to further damage the board and conclude it's dead.

[Agent24]

Re: Laptop Motherboard Repair

Having never done this myself, I may be wrong!! Wait for someone else to confirm!

But, I would think, don't apply to the DC input jack unless your short is across it. Otherwise you may blow all sorts of things that aren't shorted with too high voltage or such.

Probably what you want to do is find the part\branch of the circuit where you have found the short, verify there is in fact not supposed to be a short, and apply power there, and see what happens.

I expect you'll need a supply with current limiting. Start off with a low current and work up, keep looking for signs of overheating components.

If you go too high you could burn out a board trace, then you'd really be screwed.


And remember, components like inductors can look like shorts to a DC ohmmeter, when they're not really!

[flex1]

Re: Laptop Motherboard Repair

Hi,

Can anyone give a brief explination of how to use a bench supply to "smoke" out the shorted componant ? i know its probably not good practice but i have a couple of boards that i have extensively tested with my meter but have been unable to find the shorted part, i figure i have nothing left to loose if i damage the boards even more so might as well give it a go, do i connect the bench supply to the DC Jack input ? and what kind of voltages / amps would i be looking to use on a board that requires the standard 19v

Thanks Ste

[mattbrad2]

Re: Laptop Motherboard Repair

severach, can you walk me through your process of using a bench supply to test these shorts? Say you have a ceramic cap shorted on the opposite end of the dc jack, close to the charging circuit. Where are you applying voltages and what voltages are you applying? On a 19v (or 10-14v) rail, what voltage would you start at and how are you measuring "heat"?

[infringer]

Re: Laptop Motherboard Repair

So its safe to say some of the common tools we will use are:

Desoldering Braid / Desoldering Iron
Soldering Iron / Station
Hot Air Rework Station/ Ceramic Heater / Toaster Oven / Heatgun last resort
ESR meter
Digital Multimeter
O-Scope if you can afford one

I don't mind using redneck tools if need be I've done repairs with a heatgun and have been successful.


So a nice list of tools required for laptop repair would be of the order and here is a good start.

Benchtop adjustable power supply 3.3v 5v 12v should be the common voltages used.

[severach]

Re: Laptop Motherboard Repair

Isn't your "smoke out the shorted part" approach a little dangerous - aren't you at risk of burning PCB tracks this way?

The point of the bench power supply is to add just enough power to get the part to heat up. If a trace were to heat up I'd know that the shorted part is far away. So far all the caps have been connected with really big traces--probably power planes that I couldn't possibly heat up.

[Pyr0Beast]

Re: Laptop Motherboard Repair

Eh. I just hook up a 1.2V nicd battery there and see where it smokes.

[Agent24]

Re: Laptop Motherboard Repair

Isn't your "smoke out the shorted part" approach a little dangerous - aren't you at risk of burning PCB tracks this way?

[severach]

Re: Laptop Motherboard Repair

A common problem with laptop boards is a shorted ceramic or tantalum capacitor shorting out a single supply or the entire system supply. If 20 ceramic capacitors are in parallel and one of them is shorted, all 20 will show as shorted. A DVM will show you the list of 20, which is important to know, but it can't pinpoint the bad one. The Leak Seeker and the bench supply can. I just haven't spent the time with the Leak Seeker instructions to figure how to use because the bench supply finds them so easily and so fast with no downside. Even if a major chip is shorted the bench supply finds it easily, just as the Leak Seeker would.

The Leak Seeker measures the resistance as you place the probe along a shorted path. To a regular meter the shorted path has zero resistance. Like an ESR meter, the Leak Seeker is equipped to measure very small resistances so the path resistance is measurable. The Leak Seeker knows the resistance of the entire path and it knows the resistance from where the roving probe is placed. The probe point completes a voltage divider circuit. The closer you get to the shorted the component, lower the resistance of the lower divider and the more noise LS makes. Measuring resistance down near 0.001 ohms is not trivial and requires some setup. I haven't been forced into learning how.