Hello,
I was wondering how a valve rectifier would react to a high frequency AC voltage (atleast 50khz, possibly square wave.) My first instinct is BAD.
I know that with diodes, the reverse recovery time has a huge impact at the efficiency of rectifying high frequency ac in SMPS's, and I am wondering if a vacuum tube rectifier would experience the same problem, albeit from different causes.
Any thoughts?
I was wondering how a valve rectifier would react to a high frequency AC voltage (atleast 50khz, possibly square wave.) My first instinct is BAD.
I know that with diodes, the reverse recovery time has a huge impact at the efficiency of rectifying high frequency ac in SMPS's, and I am wondering if a vacuum tube rectifier would experience the same problem, albeit from different causes.
Any thoughts?
Not 50 kHz, but booster diodes like the PY81 and E.H.T. rectifiers like the EY51 work with 15,625 Hz saw-tooth signals (horizontal deflection and E.H.T. in TV's).
Diodes like the EA50 were used in the measuring-heads of multimeters which could measure AC voltages up to 100 Mhz (for instance in the Philips GM6008).
I would think that at 50 kHz the distances between cathode and anode in these tubes are not a problem yet (transition time wise), but I'm not sure about this.
Diodes like the EA50 were used in the measuring-heads of multimeters which could measure AC voltages up to 100 Mhz (for instance in the Philips GM6008).
I would think that at 50 kHz the distances between cathode and anode in these tubes are not a problem yet (transition time wise), but I'm not sure about this.
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Would this be doable for a standard HT rectifier tube like a 5AR4, or only for high speed signal diode tubes used for radio?
Are there any tubes of this nature capable of rectifying for HT current demands?
Very interesting...
Are there any tubes like this that are full wave recitifiers, or do they only come in half wave varieties?
I don't think so because for the function as booster/damper one diode/rectifier is enough.
But maybe 'normal' double rectifiers would do the job also. As far as I know, the special part of booster/damper diodes is their solid cathode to heater insulation, needed because of the very high voltage peaks on the cathode (the PY81 and PY500 have their cathode come out at the top connection because of that).
Addition: The capacitance at the output of a tube rectifier that runs on high frequencies should be relatively small, much smaller than the values at the usual 100 or 120 Hz.
But maybe 'normal' double rectifiers would do the job also. As far as I know, the special part of booster/damper diodes is their solid cathode to heater insulation, needed because of the very high voltage peaks on the cathode (the PY81 and PY500 have their cathode come out at the top connection because of that).
Addition: The capacitance at the output of a tube rectifier that runs on high frequencies should be relatively small, much smaller than the values at the usual 100 or 120 Hz.
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Ah I see. Perhaps using an indirectly heated cathode rectifier like the EZ81 would provide higher heater-cathode insulation than a directly heated one?
I'm going to give it a shot once I'm back at my bench, I just wanted to see if anything would melt before hand. I guess sometimes a tube must be sacrificed for the greater good...
They do it very well. I sometime ago made a smps entirely with tubes and performed OK. It was a SEPIC plus Cuk converter whose output stage was a 33GY7A and a 35W4 entering with 270VDC and outing with +/- 350V @ 20mA. It has been published in other diy tube forum. It was only in the experimental field.
diytube.com • View topic - My "Tube SEPIC II" project
diytube.com • View topic - My "Tube SEPIC II" project
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6BY5 is a full wave damper. Expensive these days though.
I'd use a pair of 6DE4 or something.
http://www.nj7p.org/Tubes/PDFs/Frank/049-RCA_Cuningham/6BY5GA.pdf
I'd use a pair of 6DE4 or something.
http://www.nj7p.org/Tubes/PDFs/Frank/049-RCA_Cuningham/6BY5GA.pdf
Oh nice. I wish there was a clear way to determine from the datasheet what the difference between a full wave damper tube and a full wave rectifier tube with indirect heating is, besides the higher peak inverse anode voltage.
Ordinary tubes happily operate at several MHz, sometimes tens of MHz.
Tube diodes have little parasitic effects, like stored charged. Their main drawback is their dismal efficiency.
I have a number of tube rectifiers; for the fun of it, I can test them and characterize them just as I would for for a fast-recovery rectifier
Tube diodes have little parasitic effects, like stored charged. Their main drawback is their dismal efficiency.
I have a number of tube rectifiers; for the fun of it, I can test them and characterize them just as I would for for a fast-recovery rectifier
Not 50 kHz, but booster diodes like the PY81 and E.H.T. rectifiers like the EY51 work with 15,625 Hz saw-tooth signals (horizontal deflection and E.H.T. in TV's).
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That is the rep rate of the sweep. The return is at a much higher frequency so that the video spot is at the LHS of the picture tube in time for the next sweep. The damper diode sees all that. The high voltage developed is rectified by still another diode for the KVs of HT.
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That is the rep rate of the sweep. The return is at a much higher frequency so that the video spot is at the LHS of the picture tube in time for the next sweep. The damper diode sees all that. The high voltage developed is rectified by still another diode for the KVs of HT.