Bad RAM slots in motherboards - how common are they, repair success?

[sfbayzfs]

I have been meaning to post this for a while, here goes finally.

I have a lot of system building experience, and generally held the belief that bad RAM slots on motherboards are uncommon. The first one I encountered was a couple of years ago - I opened up a brand new ITX celeron board and I eventually discovered that one of the RAM slots was bad. The motherboard wouldn't boot with any RAM installed in one of the two RAM slots on the motherboard - remove RAM from that slot, and the system booted fine with RAM in the other slot only. (Of course I had been storing the board for long enough that it was out of warranty, but that's another story...) I suspected a bad solder joint or tin whisker somewhere on the bad RAM slot, but my soldering iron was misplaced a while ago, and a visual inspection of the underside of the board looked OK.

I have been testing more boards than I used to over the past year, and I have found a number of other boards which have bad RAM slots, so I was wondering how many bad RAM slots others here have run into on otherwise good motherboards.

Also, has anyone ever successfully fixed a bad RAM slot, say with a solder reflow?

So far, in terms of failure modes with bad RAM slots, either any RAM in that slot is not recognized and ignored, or else the system won't boot with any RAM in that slot, either locking up during POST or black screen before POST, sometimes with beeps. Any time I have had memtest rack up errors, I have eventually traced it to an actual bad stick of RAM, but has anyone else noticed bad RAM slots causing other symptoms?

On dual processor Xeon boards I have further findings:

• If the blue (primary) RAM slot in a channel is bad, that whole channel is unusable
• If the first blue slot for a CPU is bad, that CPU socket is unusable
• If a non-blue slot is bad, usually only that slot is bad

Does anyone else have any experiences to add?

 

[EffrafaxOfWug]

The worst "defect" I've run into in a RAM slot was a couple of dust bunnies making contact marginal and resulting in obscure memory errors.

Even if I could solder, I don't think I'd ever contemplate a repair on something as complicated as the RAM slot by anyone other than the ODM. Server PCBs are typically 6 layers plus, and the traces to the DIMM slots are, I think, the densest and most complicated areas on most motherboards.

 

[StammesOpfer]

You may be able to explain your experience that if the primary (blue) slot is bad then the whole channel is bad by looking at the CPU. If you look around at used/damaged CPUs/Motherboards often times that can be an issue. I have successfully fixed a couple bent pins on CPU/sockets but I have never tried anything for a RAM slot.

 

[mackle]

I have an ITX board down to 1 stick due to a bad slot... Never even thought about trying to repair it- just live with it.