My 70 year old brain has some memory addressing errors occasionally. Right thought, wrong tube, and I'm sitting next to a box containing some 6MF8's. The 6HE5 is a 6EZ5, but the other two 6JC5 and 6JB5 are slightly different. The 6HE5 is rated for 12 watts of plate dissipation, the 6JB5 is rated for 15 watts and the 6JC5 is rated for 18 or 19 watts depending on the data sheet. Tubes bearing two, or all three numbers can be found with any one of three possible sets of guts. Some have guts with the same plate found in some 6EZ5's. They get a bit toasty when eating 18 watts in SE class A.
A related Q if I may. The 6EA4, 6EF4 etc are HV reg tubes for up to 25+kV regulation, but only specified for 1.5mA Ia max.
What limits that 1.5mA? Seems pretty puny. Is it the power dissipation from having 1.5mA with 25kV (tube is specified at 30W Pa or so).
If I would drop Va to say 3kV, can I pull 8mA Ia?
Jan
What limits that 1.5mA? Seems pretty puny. Is it the power dissipation from having 1.5mA with 25kV (tube is specified at 30W Pa or so).
If I would drop Va to say 3kV, can I pull 8mA Ia?
Jan
i suppose circlotron to have it DC coupled throughout? May I ask if you have a schematic? I am currently working on a Futterman inspired pentode OTL using the 17KV6, a pair per channel for a nice 10W into 72R load (12x drivers in series). No DC coupled though, and sometimes getting some motorboating... will do some more tests and then make an own thread for it. Still curious about yours though!
Erik
Frank in 6-3v-4a-dht-filament-supply-question #post-5873330 mentioned 5kVPP from a pair of E/PL519. It lead me to think you can use Horizontal deflection compactrons with > 7kV Vap rating such as the 6HJ5 or 6JN6 to drive Acoustats directly.
There are 12JN6, 12GE5, 17GE5 with 2 unused pins on both sides of plate pin, nothing spot on 15 or 24V. However, most probably the 12V type heater can be used in series.
Eventually grids melt if you push enough current into them. At safe grid currents you might be able to effectively double the “IDSS”, but don’t expect miracles.
Driving from the cathode? An UNSET with an actual triode?
The problem is that you might want more current than those beam triodes can provide at sane plate voltages. You can only get a lot of current at very high plate voltages. One might be better off with a modest-current HOT and run the screen down low (say 50 to 100V). With those types with 2 dead pins on either side of the plate, you can even pull the contacts out of the sockets. That will get you some more voltage capability before things arc over.
The Beam Triodes do seem to be an ODD design for a pulsed current mode tube. They have a dense frame grid that blocks most of the current capability down to 300 mA peak. Most tubes with a 2.4 Amp Htr can do well over an Amp of steady plate current. Apparently all this dense Frame grid gm so they could be driven by 5 Volts. One would think they could have settled for 10V drive to get 600 mA peak.
The normal HV tubes have hard vacuums with Tungsten etc. type cathodes to resist high energy +Ion bombardment. The Beam Triodes do have some kind of special coating on their cathodes to resist this, even though their normal TV pulsed usage limits the exposure time. Continuous HV usage in an Electrostatic speaker Amp. may cause problems with this +Ion bombardment for normal TV Sweep tubes. Can only try and see.
Maybe some of the pulse Tetrode type tubes, like GMI83 or GU72 etc. could work here. Although those are typically rated for just a bit over a KV.
There is that Raytheon RK-4D22 / 4D32 beam pentode that goes up to a KV and Amperes, no tetrode notches. None are as cheap as TV tubes though.
If I had to drive Electrostats, I think I would use a LV tube to drive a HV Mosfet cascode above it. Same current as the tube puts out. That wouldn't be much like a low Z Triode drive however, without some local N Fdbk. The Beam Triodes, or Sweep tubes either, don't look anything like real low Z Triodes for Zout. Just mount them on the chassis top for show, so much Safer.
The normal HV tubes have hard vacuums with Tungsten etc. type cathodes to resist high energy +Ion bombardment. The Beam Triodes do have some kind of special coating on their cathodes to resist this, even though their normal TV pulsed usage limits the exposure time. Continuous HV usage in an Electrostatic speaker Amp. may cause problems with this +Ion bombardment for normal TV Sweep tubes. Can only try and see.
Maybe some of the pulse Tetrode type tubes, like GMI83 or GU72 etc. could work here. Although those are typically rated for just a bit over a KV.
There is that Raytheon RK-4D22 / 4D32 beam pentode that goes up to a KV and Amperes, no tetrode notches. None are as cheap as TV tubes though.
If I had to drive Electrostats, I think I would use a LV tube to drive a HV Mosfet cascode above it. Same current as the tube puts out. That wouldn't be much like a low Z Triode drive however, without some local N Fdbk. The Beam Triodes, or Sweep tubes either, don't look anything like real low Z Triodes for Zout. Just mount them on the chassis top for show, so much Safer.
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I have a schematic made in the old txt way for my own use, made with edit.com. If you really want it send me an email to lw1dseATgmailDOTcom or lw1dseATyahooDOTcom.