Midas m32r power supply problem (psu)

Few months ago i buy a mixer from someone on ebay, he state that the board was a unit return from midas, i use it on my home studio and wasworkinggreat but 3 weeks after start to have some problems, suddenly start to make a pop sound and all the input meters star to go crazy and all the. Output reproduce the same pop sound even after disconnecting everything from the board, i have to turn off to make the problem go away but after couple times is just making the sound. Does anyone having this problem.