NFW is that a 650W power supply, more likely 200W on a good day with a following wind. The transformer is similar in size to ones I see in 200-250W switchers, and it will never deliver 3 times the power, let alone the rectifiers and the capacitors on the secondary ( let alone the primary side) being rated to actually handle that and not explode.
Consider the primary side is pretty much plain with no PFC aside from that passive PFC inductor ( and that can be a fake as well in many cases, copper is a lot more expensive than steel laminates and a 4 turn wire through with a lot of tape padding) and the main switching transistors are going to explode with 3A average through them. It will do as a 200W PSU, but anything more is not going to work.
Is there a supply to the SMPS controller , which is a pretty generic part, and if so is it oscillating. The drive likely is being carried over by the 3 optoisolators, so if they are not working, or if the main transistors or the components around them are faulty you will get the output you have as one transistor is not turning on when needed or is dead short and has blown the other open.