One RAM slot dead?

Hi,

I tried to upgrade the memory of my 2010 mini.

Took the 2 x 1GB out, 2 x 4GB in, restart and just one beep.

Took all out, cross checked, tested a lot of times with various DIMMs.

Finally and that's it: Only the DIMM in the upper slot works. No matter which.

One DIMM in the lower slot - beep. Two DIMMs - beep. One in the upper - chime and start... No matter which DIMM.

I did smc and pvram resets.

I don`t see any faulty contact inside of the slot, there´s no dust or anything else.

I'm worried that I killed somehow the lower slot, but how? And what to do now?

Any tip welcome!

Thanks!

crisb