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Well, I got things settled in and listened for about an hour
today. Again, no smoke :-) and some good sounds.
I'm liking what I hear so far.
I connected the primary of the 300B power supply section to the
switching system, not the variac.
I kept the primary of the plate transformer connected to the variac to
control the output voltage. I had been getting about
1240VDC on the plates of the 845s and that's pressing things, in my
opinion. My bias supply was unable to produce
enough V- to get the tubes under 60mA. With 1KV, I have control
of the tubes from zero current to way
I plan to operate them at 60mA.
Here's a shot of the 866A MV tubes at work.
Behind the 866As you can see the 6D22S damper diode that I use for
slow-start purposes. They take about
30 seconds to warm up and conduct fully. I have them in the
ground line, so they don't see much DC.
Here's a shot of the 816 rectifiers I'm using for the 300B driver
section. I need to change some resistors
in this power supply to get a little more DC. The Kenyon chokes
have a higher resistance than I
had thought initially.
Here's my trusty Simpson meter showing half of the B+ at 510V. I
have a 100K 50W bleeder resistor
(made from two 50K in series) across the final caps, so I measure at
Here's another shot of an 845 at work.
I'll be adding more to this site as the project progresses. If
you any questions or comments about this amp, they're
certainly welcome. Email me at email@example.com