EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: bogdan2014 on April 07, 2020, 10:18:39 am

Title: Motherboard 5V rail issue
Post by: bogdan2014 on April 07, 2020, 10:18:39 am
We have this older computer at work that has a strange issue. When powered up, it doesn't POST or boot, but every LED that lights up "pulses" like the 5V rail was pulled into protection. I have checked it with a multimeter and indeed the voltage drops in cycles, but the other rails are absolutely fine. The power supply does not go into protection itself, it continues to power the rest of the computer (fans and hard drives work). Something probably pulls the rail but not enough to trigger the overcurrent protection. I have replaced the power supply and the same issue occurs.
I have eliminated almost everything that might cause an issue outside of the motherboard, even the RAM, I have also replaced some leaky caps. What can I possibly do to salvage it?
I would scrap it but it's the only one we have that works in that configuration.
Title: Re: Motherboard 5V rail issue
Post by: Rasz on April 07, 2020, 11:52:02 am
What can I possibly do to salvage it?

start with model of the board
remove everything out of the case and plug just the bare minimum