Years ago I was told of a method for cleaning the contact fingers of ram sticks and it seems to work well. Instead of using alcohol use a piece of clean brown paper bag like you would get from the grocery store to swipe and clean off the contacts. The paper is rough compared to newspaper or printer paper but not rough enough to remove very much of the gold on the contacts like even the finest sand paper would do. I've also used a folded up piece to run through the actual memory slot on the board making sure the last folded edge goes in the direction of the swipe so it can't snag the contacts.
Used a white pencil eraser on some ram sticks and they came shiny clean in no time, now it always posts like it should
The eraser is the standard method and always work. It's also possible to use a money bill, which is abrasive. It works and is a handy alternative when you are in the middle of nowhere and there's no eraser at sight. Unfortunately, in my country we don't use anymore the brown paper bag. We use soft plastic bags that kill our sea turtles. I use coffee filters (with isopropyl alcohol) to remove thermal paste from processors and coolers. I guess it may be used (dry) to clean slots. Again, it's hard to know if the coffee filters in my country are similar to the ones in other countries. But anyone willing to know what is safe or not can use your post as a reference... Thanks!
One week running my rig with an ASUS new motherboard. The processor was tested with the Intel Processor Diagnostic Tool. The RAM is OK. Stress test OK. Everything's fine, with the exception of the Intel mobo, which lasted only two years... I'll test it again someday, with another processor. Thanks everybody!