Just posting this as a "community service" announcement to help prevent others from making the same mistake.
The issue: mis-estimating the current draw on the secondary of a power transformer. I have been mistakenly treating the current draw of the ultimate load (tube stages) as the current draw on the PT. TOTALLY WRONG! With a cap input power supply (cap after rectifier diodes), the first cap sees a ton of ripple voltage resulting in a lot of ripple current into the cap. I only recently figured this out when puzzling why my BeePre rebuild has some slight chassis vibration and fair bit of heat where I installed separate low voltage filament supply transformers for the 300Bs. "What's wrong with these things ... each 300B only draws 1.2 to 1.3 A and the trafos are rated for 2A continuous current". And then it hit me, "Oh s&*t, that's not right". Sure enough, looking at the PSUD sim of my CLC filter that goes before the fil reg, actual current draw on the trafo is 2X the current draw of the load: 2.6A versus 1.3A.
No wonder my LV trafos are vibrating and getting hot! I am replacing them with trafos rated for 4A.
Happily, just changing the capacitance value of the first cap doesn't seem to pose much risk. Doubling the stock capacitance of the voltage doublers in my Kaiju had negligible impact on current draw -- at least according to my PSUD sims. [Edit: but this is only true after the caps have initially charged; increasing the capacitance will increase inrush current at turn-on and could cause blown fuses].
cheers, Derek
