UPS & PSU

Hello All! The power was turned off here recently, all the equipment began to work from UPS... In particular AON connected through a regular AT power supply specially purchased for AON. And a problem arose - somehow this power supply produces so much noise when operating from UPS According to the power supply (approximately 50-100Hz) you can’t hear anything at all in the handset. How can I fix this? There are capacitors at the output of the power supply... Put a 5V capacitor at 150000uF*16V? Will the power supply withstand charging it? PS. I tried to connect the radiotelephone - the same thing :( Best regards, Evgeniy.