| Electronics > Projects, Designs, and Technical Stuff |
| Overhauling high voltage vacuum tube (valve) power supply |
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| proschuno:
--- Quote from: calexanian on February 16, 2014, 04:33:05 pm ---Believe me. Put an ac meter in there and you will see much higher ripple than that! The resonance is supposed to be less than 120hz. Far less. It's not a dc filter in a traditional seance. It's to provide an ac component to the current flowing through the choke to provide proper filtering there. You just have to play with those circuits to understand. Look up the section in the RCA radiotron design handbook under power supplies. It's the best description and explanation of how those circuits work anywhere. You can see how they did it before our modern stuff. I highly recommend that book to everybody. Just the basic circuit theory in there is better than any modern textbook. --- End quote --- For the radiotron designer's handbook, would this be what you're talking about? http://www.tubebooks.org/Books/RDH4.pdf Oh, and in general, can anybody tell me why the cathode of the 6x4 is connected to one of the hot leads of the High voltage leads? Never quite understood that.. |
| richard.cs:
I would be inclined to replace the electrolytics but leave the oil-filled caps. They tend to last forever unless they physically leak oil. Film caps would be a perfectly acceptable replacement I just don't consider them necessary. One change that might improve performance is swapping the OA2's for a zener-string but personally I wouldn''t bother. If your purpose is to overhaul the supply and make it work as well as it did when do then just go with minimum change, if you want a better performing supply then you'd be best off starting from scratch. One thing to watch out for if you use film capacitors for high voltages is they tend to exhibit charge recovery much more than electrolytics or oil filled capacitors do. You should make sure that bleeder resistors are present and not open-circuit. |
| N2IXK:
--- Quote from: proschuno on February 17, 2014, 02:18:53 pm ---For the radiotron designer's handbook, would this be what you're talking about? http://www.tubebooks.org/Books/RDH4.pdf --- End quote --- Yes, that would be the one referred to. That was "the" classic circuit design manual for the vacuum tube era. --- Quote ---Oh, and in general, can anybody tell me why the cathode of the 6x4 is connected to one of the hot leads of the High voltage leads? Never quite understood that.. --- End quote --- That is where the 6X4 gets its AC input voltage. It goes into the cathode rather than the plates, because the 6X4 is being used to develop a negative bias voltage. Both plates are tied together because the tube is being used as a half-wave rectifier. |
| calexanian:
--- Quote from: proschuno on February 17, 2014, 02:18:53 pm --- --- Quote from: calexanian on February 16, 2014, 04:33:05 pm ---Believe me. Put an ac meter in there and you will see much higher ripple than that! The resonance is supposed to be less than 120hz. Far less. It's not a dc filter in a traditional seance. It's to provide an ac component to the current flowing through the choke to provide proper filtering there. You just have to play with those circuits to understand. Look up the section in the RCA radiotron design handbook under power supplies. It's the best description and explanation of how those circuits work anywhere. You can see how they did it before our modern stuff. I highly recommend that book to everybody. Just the basic circuit theory in there is better than any modern textbook. --- End quote --- For the radiotron designer's handbook, would this be what you're talking about? http://www.tubebooks.org/Books/RDH4.pdf Oh, and in general, can anybody tell me why the cathode of the 6x4 is connected to one of the hot leads of the High voltage leads? Never quite understood that.. --- End quote --- Thats the one. Also. I don't know who started the idea that oil filled caps have high ESR. Tell that to the many thousands of them still being used in discharge welding service! They are still used for big stuff. Radio transmitters, BIG welding equipment. X ray supplies, anything really high voltage. Chicago Condenser is still in business http://www.capacitorindustries.com/ Have a look through their website for fun! |
| calexanian:
They actually have a foil film replacement for you. have a look at the CMP-805-6C. Looks like an old style one if you want to keep the warm fuzzy feeling of an old oil can. Might actually have to design something just to get one to play with! BTW. I am not trying to be snarky or obstinate in any way.. Many of these technologies were working well before we were born and will continue working well after we are dust. Just because something is old or deemed to be obsolete, or has a bad name based on feeling rather than science (Leaded glass for example) does not mean it still can have a place or be useful. Don't forget. One of the largest use for tubes still to this day are RF bombarders in the preparation of materials for semiconductors! hahahaha http://www.capacitorindustries.com/capacitors/high-voltage-dc-capacitors/cmp/default.html |
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