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Trying to breadboard the 6bq5 amp shown below, but I am not sure why he only shows two grids in his schematic when the tube manual shows three. How should I interpret the connections he shows in his schem?
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G3 is internally connected to the cathode.
Ok. So is he showing G3 or G2 as the upper grid line in his schematic?
More often than not pentodes and beam tetrodes are graphically represented as tetrodes.This means that the "uppermost" grid is g2, because g3 is not represented in the symbol.
The reason for this is that in most pentode and beam tetrode tubes g3 (or the beam former in beam tetrodes) is internally connected to the cathode, and does not have it's own pin.
Basically, you can only make 2 choices here:
1)connect g2 to the anode, which will create a "triode mode" connection,
2)connect g3 to the anode, which means you will connect the cathode of the tube directly to the anode, bypassing the tube itself...The latter will most probably blow a fuse, provided you have installed one...
My father used to say that with electricity you can only make one mistake. Be careful!
*******
http://rh-amps.blogspot.com/
Edits: 09/14/14
You had it right Alex. I did it like you suggested and it works fine. I am surprised at how good it sounds too! But then it is such a simple design the sound depends on the tube and I have always liked the sound of a 6bq5.
Going to have to put the other channel together and plus up the psu. I do believe this little amp has possibilities with my Altec Granada's.
Thanks for the help!
Thank you Alex, for a answer that I can understand and that answers my question. I will be careful believe me.
Vinnie, I'm very concerned about someone at your level working with HV power supplies and amplifiers. Your experience is similar to mine at the time I started building electronic kits. Even after several of those, I was nearly electrocuted more than once after I started building from scratch. Honestly, I'm lucky to be alive. I strongly suggest that you consider a more gradual approach to this hobby.
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Buy Chinese. Bury freedom.
I appreciate your concern, but I consider spending the last 15 years restoring vintage gear, assembling kits, and for the last ten years, building from scratch to be a pretty gradual approach to the hobby.
I am really not sure why you feel that if someone doesn't understand the theory they can't follow a schematic or have enough sense not to put their hands where they don't belong.
I take all the recommended precautions and I am very careful. Just because an electrician doesn't know how electrons work doesn't mean he can't wire a house properly if he follows the wiring plans.
Edits: 09/14/14 09/14/14
"I am really not sure why you feel ... not to put their hands where they don't belong."
In this case, I believe they don't belong near circuitry with high voltage. I don't know what you were doing for that 15 years, but clearly it wasn't enough to be at the requisite level for this work. This isn't the first time you've claimed to have engineering experience, only to show a fundamental lack of knowledge in this area. A word to the wise Vinnie, it's easy to get killed doing this stuff.
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Buy Chinese. Bury freedom.
In the first place I am a CE not a EE, and I have never claimed to have EE training or knowledge. In the second place you don't seem to know the difference between "book learning" and hands on experience. The enclosed photos are of the diy gear I currently have, all of them built from scratch by me. In addition over the years I have bread-boarded at least 20 other amps and preamps.
Do you really think someone could build all of this without having a pretty good ability to follow schematics? And that is ALL that is necessary if you have a good design, no matter how much you like to tell yourself otherwise.
Edits: 09/14/14 09/14/14 09/14/14
I'm glad to see you've got that under your belt. However, my concerns are not for what you've built, but rather for what you've learned. Be safe, that's all.
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Buy Chinese. Bury freedom.
Which grid would you expect to be connected to the plate for a triode connected pentode?
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