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Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Thats a nice brick!
Here is some parts from a 50-60 year old b/w television set i got from a friend, I only recieved the frame with the electronics on. It was in a non-working condition, so took it apart to be able to bring it home on my bike.
The coolest thing about the components are the danish made capacitors, resistors and switches. Only tubes and a few other things are from mostly Germany :)
Abit of a related question, will I be able to drive a PL36 tube at 1.5MHz? I cant find any values in its datasheet except its a line output tube for televisions.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
I finally got my 100MHz Op Amps for the DC - 10MHz preamp ( for driving these power amps ) YAY! so Im happy. They are LM6181IN amps.
The amp to the right is a class B amp that I was playing with for initial testing purposes and I think it will push 20W, I have yet to really characterize it but I will do that after full integration with the preamp.
The amp to the left is my power brick, and I do mean power brick! It has 6 200W Motorola power transistors capable of 20MHz operation and I want to get these guys really pushing the power hard. I was trying to get it going with a CCS and all that stuff ( with some 30MHz transistors ) but I ran into bandwidth problems above 1MHz. Emitter degeneration and compensation are haunting me!
I'll just have to see how many stages it takes me to get 100W out at up to 5MHz. I know some of you guys would laugh at this "audio amp" approach, but I seriously can't get this thing's gain stable from DC to 10MHz with a class AB setup. What I've tried on the brick would be awsome as an audio amp with the CCS and all, but it really won't work above the 1MHz range. So I'm just going to try some more class B configurations and see where I end up. If all else fails I'll buy some real RF parts and go from there. This is my first real RF amp after all.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
wrote ... I seriously can't get this thing's gain stable from DC to 10MHz
I'm not surprised, I think you are crazy for even trying If you want power at 10MHz from cheap plastic-packaged thingies, you need to follow the kinds of approaches that these guys use:
BTW, nice brick c4r0! I bet somewhere in Poland there is a train driver wondering why his electric train won't start this morning
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
I'm still buying books on RF amps and I haven't gotten the book on switchmode RF amps just yet, but the main goal of this amp (and I don't know if the switchmode one will do this ) is to preserve the waveform. I have a GR tube amp here capable of ~15W of power but it still needs work. The original design assumes that the phase splitter output is balanced and its not even close, so I'm having to redesign the front end. Other then that, I have a few more books to buy, and probably a bunch of MRF parts. I know the preamp will go to 10MHz so that's a start, I just don't know where the power amp will crap out at yet.
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