SURTA1500XL electrical buzzing sound

[BillP]

I have theree news SURTA1500XL serials JS10...with a strong electrical buzzing sound when connect the load (any load); the sound is more strong with more load.
If the load is disconected the sound disappears. Is difficult to detect the component that cause this sound on PCB
Any one had a similar problem?

[BillP]

what are you plugging in specifically? loud buzzing when load applied makes me think [ground loop|http://www.epanorama.net/documents/groundloop/basics.html] almost immediately.

[BillP]

I used resistive load from 150 to 1000 watts, and computers too. Other SURTA1500XL doesn´t have this noise when apply the load.

[BillP]

Exactly. I have three brand new ones with the problem. The others is working good without any buzzing sound

[BillP]

so three brand new ones do this but you have others that do not?

[BillP · Accepted solution]

hm ok, can you tell me the numbers after the JS10 on all three of those please?