I would like to RMA it but we are out of support as we have this unit as a donation.
Give it a try. 2960S is covered under Cisco Enhanced Limited Lifetime Warranty. So this means you don't need to have a valid Service Contract. All you need to do is ensure the appliance is registered to you. Contact the person who gifted this appliance and see if he/she/they can contact Cisco.
Word of Caution: Cisco Enhanced Limited Lifetime Warranty is a very "thorny" issue inside Cisco. (John Chambers, Cisco CEO, announced this to the whole world in retaliation to HP's own Limited Lifetime Warranty.) Cisco's contractors, the Entitlements Team, will try their very best to deny you this obligation. Be prepared to fight the Entitlements Team with common sense. I have made several RMAs of switches and APs under E-LLW/LLW and this is their standard procedure.
Thank you for the advise. I will try to communicate with donator.
In the meantime I was hoping to try all possible ways to fix the issue. Are you aware of any "secret" logging facility that I could activate or any good reseller where I could ask for Power Supply Unit replacement?