Hi again,
The power supply for my homebrew amp is looking pretty good. Using a
variac I increased the primary voltage with the secondary shorted by
an ammeter until it was delivering 750 mA. I ran it like that for an
hour and it barely got warm to the touch. (The variac got pretty hot,
however. It stank, too.) I've chosen a primary tap that gives me just
under 4000vdc with no load (other than the big bleeder resistor.) The
only way I can see to really load test the supply is to disconnect the
internal B+ on my SB-220 and use my homebrew supply. It's a hassle,
but it will let me verify that the regulation is OK.
With the power supply looking good, I'm turning my thoughts to the RF
deck. I picked up an inductor that looks like it might be OK in the
tank, but I have no data on it. It was made by Illumitronic
Engineering in Sunnyvale, CA, and says "air dux PI #195-1" on the
plexiglass support. Does anyone have any data on this inductor? By
itself I think it would cover 80-10, so I'll have to add more
inductance to cover 160. I'll make some measurements this weekend.
Another question. I have access to a vector impedance meter. I know
what the plate impedance will be for the tubes I've chosen. Can I
terminate the tank output with 50 ohms and use the vector Z meter to
select and verify the taps on the tank coil? It's an easy thing to do,
but in practice will it result in the correct tap selections?
Thanks for all the good advice and encouragement on my amp project.
I'm having a blast, and learning something new everyday.
73,
Doug, KF4KL
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