Display Flicker After RAM Upgrade? Check PSU Outputs!

March 4, 2013 | By Rakhitha | Filed in: Tech.
These RAM are now officially retired.

These RAM are now officially retired.

In case you are wondering why your monitor flicker and computer crash after a hardware upgrade, this might be the answer. New hardware can drive the voltage bellow 5% tolerance level required to run the PC smoothly. You can check the voltage level in BIOS or with a Multimeter. But don’t rush to buy a new PSU. It is most likely a loose power connector.

Here is what happened. It’s a bit long. I decided to give a RAM upgrade to the old computer that we are having. I bought  two Samsung 1GB sticks (DDR 400Mhz) from a local refurbished RAM shop. After the upgrade computer simply kept crashing while loading windows. If I plug just one of the memory cards, computer boot up, but it was very unstable. Display kept flickering and eventually it crashed.

I took the RAM cards back to shop, but they ware working just fine. But anyway I got them replaced with a different brand. With those two RAM sticks computer booted up but display was still unstable and sometimes it just crash.

After searching the web, it seemed to be a common problem. But pretty much every post I found suggested that I have busted the VGA card or the RAM is bad or incompatible with VGA.

Interestingly, flicker happen when the hard disk is active. So I checked the voltage levels. BIOS reported that 3.3v rail is at 2.86v and USB voltage at 4.1v. First of all, these numbers can’t be right. Because if it was true, computer should not even start. But they ware way bellow what it used to show. I tested by connecting just one memory card and the voltage was about 0.1 ~ 0.2v higher.

First I though it was the old PSU being over taxed. But after poking the power connector to the motherboard with my finger, voltage on 3.3v rail increased to 3.1v. After a good cleanup of power connector to remove dust and dirt it collected over the years, 3.3v rail is showing 3.28v and USB power is at 4.98v. And the computer is running very smooth :).

Here is the thing with bad connections. They create resistance in the power line. As a result, even a slight increase of power consumption will significantly drop the voltage. Therefore if your computer is unstable after an upgrade, check the power levels and connections first. Specially if it is old and dusty. Hope the next guy to have this problem will not have to waste as much time as I did :).

Btw, I am not responsible if you electrocute yourself or destroy your computer. Make sure the power is off,  mains power cord is disconnected, and equipment is well grounded before you touch anything.



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