Question Burning Smell on two motherboards

[greyfox1993]

HI everyone I really would love some help here, so I brought two asrock motherboards from Ebay One of them was used and the other was Seller Refurbished but both of them gave off a burning smell so I sent them back. The odd things is though I use a MSI 760Gm p23FX and there is no burning smell.

Specs of PC at the moment

CPU - FX6300 ( No Overclock)
MB - MSI 760m- p23FX
RAM- Kingston 8GB
GPU GTX960 4GB
PSU - Corsair GS600 but also used a Corsair 430

 

[SkyNetRising]

And what is your question?