R51 Motherboard issues

[hellaxe]

Hello people:
This is the thing and not related with the other topic.
I was working and suddenly the monitor went black. It was a very hot day so I thought it was from the heat.
Wait some minutes and then try to start the machine.
Nothing. The cooler starts, stays working but no booting. The IBM image doesn't show up.
I have some expertise so i start to disasemble some parts. HD, DVD, mems, pcmcia, everything. I rip everything off that could made these problems.
Finally i remove the motherboard clean it with alcohol and put everything together.
With this i could bring it to life again
But 4 days after the same thing happened. Yesterday i made the same procedure and it start again but when i touched the VGA-out conector in the mboard.... black out again.
So i think it's a stupid component that's not welded properly or something like that.

Questions:
- Does anybody have same troubles?
- Where do i start checking?
- Other ideas.
Thank you

PS: it's difficult to find some good companies in Portugal to do this kind of job without charging a LOT. IBM charges even MORE.

[vlyne]

You’re not alone hellaxe! Mine (Intel graphics) was in the no-boot but-lights-on mode when I got it. I stripped it down and gave it a good clean and got it working again. Managed to flash bios with latest version, get the operating system installed and working, then after being on for a few hours it died. No amount of coaxing would get it going again. I stripped it once more and found a blown SMD capacitor (underside, under black tape next to s-video connector). Replaced this with another (had to guess at its value) but still no go. I suspect there are other components that are blown. I’ll have another go when time permits. I’ve checked for loose inductors so next up is to check all the major capacitors; then the transistors. On other motherboards, I’ve found that if there is one blown capacitor, there’s likely to be others nearby. Good luck!
Cheers

[hellaxe]

Thanks.
Now I'm disappointed.
How does a condensor like these look? Blown up completely or just a smelly think and some burns?

[vlyne]

They come in different shapes and sizes but the main ones are the larger black rectangular ones or light yellow-brown ones - labels start with a "C". Burnt ones should be obvious but they generally look normal so you have to test them in-circuit. With a resistor test you should see the "resistance" varying and it depends on whether the capacitor is charged up or not. If there is a charge, chances are it's good. BUT, poking around with a resistor test may also corrupt your CMOS/BIOS so be careful. There are instructions on the web on how to test capacitors - see for example: testing capacitors

It could also be a cold solder and those are much more difficult to find/diagnose. The standard test if the "flex test": trying flexing gently the board in various ways and putting pressure on various parts (after grounding yourself).

If I get a chance to have a go at my R51 and find anything I'll report back.
Cheers