[Amps] looking for design

Ulf Tjerneld star at frizon.org
Sun Feb 22 08:12:30 PST 2009


Hi All,

I did experiment with some home built tube amplifiers back in the early 
80's, but I was never really successful. Mostly, because it was hard 
locating surplus parts here in Sweden and my high-school economy didn't 
allow for buying brand new parts. The only thing I got running was an 
amplifier with a single 813. I think I got about 200 watts, and I could 
never run it below 15 meter because the capacitors wasn't big enough. 
Later on I drifted away from amateur radio and electronics design - hard 
to find room for that when I moved to a student room. Recently I came 
back to amateur radio and I started with building some antennas and I 
felt the joy from last time I was active! So, now the thought came to me 
that maybe it was time to fulfill my dream of building a tube amplifier 
- doing everything right this time! First I bought a box of scattered 
parts, including a couple of vacuum capacitors, a transformer and a 
GS35B, but I quickly discovered that the plate transformer only 
delivered 1700 volts, too little for the GS35B. At least if I want to 
drive it to its full potential. After thinking a little bit, I decided 
that instead of getting a new plate transformer, it was a better idea to 
build something around the existing transformer. 2400 volts DC would be 
perfect for the boxed 813’s I kept all those years. And as I see it, 
maybe this a better beginners project? So, now I’m looking for a design. 
I have some old ARRL-handbooks with a couple of 813-designs. But I would 
like to see more of what is out there! That’s why I’m trying this forum 
to see if I can get any ideas about 813-design. I’d be happy for any 
suggestions!

Thanks and 73’s de Ulf/SM0NOR






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