I think some component turned bad when you exercised the scope. It may have been stored unused for a long time.
It can be a cap or diode, we don¡¯t know yet. You have come this far which is a good start. You can repair it, sure, but it requires some serious thinking first.
Most likely there is only one bad component. You need to find out if any of the regulated outputs (+50, +15, +5 etc.)
Is overloaded. Is it possible to disconnect one output at a time and see what happens? Be careful.
