Sounds like you need your amp gone over properly, cleaning some points and tube swapping sounds like a low budget job. If the amp had a problem before, it might just have not been putting out the power it could have, and sorting that could give you the juicce to blow cabs, and when a cab goes, its impedance also goes wrong, either way, so could have taken something with it. If you amp does burning smell, it needs to be properly looked at.