[462ron]

Hi, The first rule whenever working on a set without a power transformer which your set is this type, is to use an isolation transformer for safety reasons. Most of these types of sets have the chassis or a floating B- connected to one side of the AC line. This set is a little different as it uses what is known as a voltage doubler for the B+. I know you said you are using a variac but many of those aren’t isolated from the AC line. If your signal generator has a 3 prong plug so it is grounded and you connect the ground from the signal out put to either the chassis or B-, you have put a direct short to ground depending on which way the AC plug is in the receptacle. Thus the need for an isolation transformer and is the reason why it cooked your generator and made the dim bulb light up.

Ron