Who can help me to find authorized companies which repair PSUs of the Speedtronic Mark VI like IS2020LVPSG3A (GE). Who can give me a fair quotation?

 

GE has a "repair & return" program.

Or you might try contacting one of the advertisers here on control.com, Gas Turbine Controls Corporation, to see if they would repair your power supply or know of someone who would.

But, if you're failing a lot of power supplies, are you having a lot of ground problems? Are the power supplies overloaded? Repairing power supplies and having to keep repairing them is a sign of deeper problems, and you will spend a lot of money repairing power supplies if you don't resolve the underlying cause of the failures.