I bought a home brew amp with 2 x 4-250A tubes on ebay. Nicely built but it
is grounded grid.
The filament transformer is 10 volts with no center tap and the two five
volt filaments are wired in series. The B- is thru a meter to a resistor
across the filaments.The article with the amp suggests the bias is for class
B operation.
I want to convert the amp to a tetrode circuit running AB1. My first
question is the B- point. I will use the same filament transformer and I
want to know if connecting a meter between ground and the connection between
the two filaments in series will work OK. I can't see why not. But you folks
know a whole lot more about this stuff than I do.
I need to build a power supply and from what I can see, using the tetrode
board from IFWTech / G3SEK will make life a lot easier. I was planning on
getting the screen bias voltage for the tetrode board by taping across the
lower caps in the power supply. Not much current is drawn so I don't see
that this will cause a problem. What do you think?
Mark, NØOKS
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