so i have a Recordex cs-4000 to fix. the problem is that a few moments after it turns on and works, but after just a couple seconds, there is a crackling/sparking sound and a terrible "burning plastic/electronics" smell. what could the problem be? i haven't fully disassembled it yet, it's pretty difficult to take apart and weighs a ton. EDIT: The problem was an old transformer sparking and burning, and I believe this was caused by a faulty rectifier. What diodes should I use as replacements?