|"Tested power supply (PSU) which failed the tests"|
I'm curious how you did that because there is no way for the average user to properly test a PSU without the proper test equipment. You might be able to check voltages with a multimeter (5%+/- tolerance is OK) but there's no way to test amperage.
The beeping is the clue. What is the pattern? See if it can be found at the following site. I know it's not for your model but the codes should be the same.