Cool, i just checked my stach of tubes, am selling off my stuff, but no PD500 or anything like it, only PL509 and 519, but those are only good for up to1.8kVpk, maybe 2kV max.
Used some of those with 1.2kV one phase transformer feed, no dc smoothing, just raw after the rectifier and some rf-filter,
for a experimental rf-heater. Did not try to go any higher than that.
Used some of those with 1.2kV one phase transformer feed, no dc smoothing, just raw after the rectifier and some rf-filter,
for a experimental rf-heater. Did not try to go any higher than that.
why? Max voltage depends on the pulse repetition rate,pulselength, and anodetemp, I guess. I fed them from rectifier direct, from rf pii filter to the rf choke to the anode, gotta add the rf peak voltage of the tankcircuit to that.
expearienced radioamateurs adviced not to go over 1.8kV, better to stay even below that. And i thinck they blew up a few tubes to get that expearience, so I took theyr advice.
expearienced radioamateurs adviced not to go over 1.8kV, better to stay even below that. And i thinck they blew up a few tubes to get that expearience, so I took theyr advice.
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Anyone who uses PL519s for ESL direct-drive amplifiers doesn't quite follow the datasheet, that's for sure, but it is still a mystery to me how you reach the conclusion that in amplifier use they can handle 2 kV peak and no more than 2 kV peak.
How do you know that 2 kV is the maximum and not 3, 4 or 5 kV?
How do you know that 2 kV is the maximum and not 3, 4 or 5 kV?
I have used those PL519 for DIY AM transmitter on 1,6-1,8 Mhz pirate band , two tubes in parallel , DC supply was 1,2KV , RF class C , g1-RF driven , anodes and g2 AF modulated ,cathodes & g3 grounded , producing very high output RF voltages on tubes anodes in range of several KV for sure , that transmitter working for couple of years without of any problem ,
but when I raised B+ voltage to about 1,5KV just a very slight misalignment of anode tank resonant circuit blew both tubes instantly by frying cathode internal short wire link to internal cathode output base pin , that short wire link blew like some sort of fuse in the vacuum ,
but the real question is how those PL519 or simmilar Russian counterpart TV tubes will work on audio amp.?, on grounded grids linear regime with anodes standing on about 4KV-DC ? , honestly I have no idea , maybe will work very good , but maybe will blow instantly ? , on the other hand I have very positive experience with C1150 tube and also with C1111 tube ( 5D21 or 715C) which is almost the same as Russian GMI-83 , working in similar AM transmitter with B+ up to 2,5KV without any problem , taking some incredible working points abuses without to fail ever .
but when I raised B+ voltage to about 1,5KV just a very slight misalignment of anode tank resonant circuit blew both tubes instantly by frying cathode internal short wire link to internal cathode output base pin , that short wire link blew like some sort of fuse in the vacuum ,
but the real question is how those PL519 or simmilar Russian counterpart TV tubes will work on audio amp.?, on grounded grids linear regime with anodes standing on about 4KV-DC ? , honestly I have no idea , maybe will work very good , but maybe will blow instantly ? , on the other hand I have very positive experience with C1150 tube and also with C1111 tube ( 5D21 or 715C) which is almost the same as Russian GMI-83 , working in similar AM transmitter with B+ up to 2,5KV without any problem , taking some incredible working points abuses without to fail ever .
As I said in #124, 1.8kVp was the peak voltage from the 1.2kV transformer. A 1.2kV transformer FEEDING the rf-oscillator. 1.8kVp unsmoothed dc PLUS high frequency output on top of it.
So the tube has to handle at least double of that, or more, and that at high power power input, considerable above 100W of unsmoothed dc,
the way big industrial dielectric heaters are done. Only differenc, i had no 3 phase supply, only 1 phase, industrial rf-heaters use 3 or 6 phase rectification.
It was a experimental mini rf-heater to find out the dielectric heating properties (wood glueing) of pangapanga and other tropical woods that are difficult to glue.
Expearienced radioamateurs told me not to go over 1.8kV, better to stay even below that.
I thougth they blew up a few tubes to get that expearience, so I took theyr advice.
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Good morning Jan,
Is the Eimac 15e suitable for your project ?
Potent miniature power package. Fun triode !!
I took monoblocks with it's larger brother (35TG) several times to the ETF; great sound .
I know Xander has 16 of the Eimac 15e's available (including original sockets etc).
Just let me know.
Regards, Reinout
Is the Eimac 15e suitable for your project ?
Potent miniature power package. Fun triode !!
I took monoblocks with it's larger brother (35TG) several times to the ETF; great sound .
I know Xander has 16 of the Eimac 15e's available (including original sockets etc).
Just let me know.
Regards, Reinout
Mornin' Reinhout. I looked at those 15e's but it seems Pa is limited to 20W.
I need about 80W total. I also like to avoid grid current, that needlessly complicates the design.
I am now looking at two 6LF6* in parallel, choke loaded, at about 3600VDC B+.
Jan
*There are several versions with heater voltages up to 26V.
I am researching prices. Anybody has a dozen or so available?
I need about 80W total. I also like to avoid grid current, that needlessly complicates the design.
I am now looking at two 6LF6* in parallel, choke loaded, at about 3600VDC B+.
Jan
*There are several versions with heater voltages up to 26V.
I am researching prices. Anybody has a dozen or so available?
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Maybe to help narrow the suggestions, do you think you'll be able to use valves without a separate cathode (just a heater/filament)? This would open up the choices to "transmitter" valves and their generally better high voltage design, but at the penalty of a flying heating power supply.
Another question might be, would you be willing to provide a G2 power supply for pentode valves? This would need to be a (not too demanding) current source bypassed to cathode (or maybe signal ground?). CCS only needs to be large compared to reciprocal of Gm, maybe just a resistor. Transmitting pentodes will never have a G2 voltage rating large enough for your use, so cannot be triode connected. The advantage of pentodes is that the cool kids ignore them, so excellent candidates, like the 4E27 family, are "a drug on the market", so affordable.
All good fortune,
Chris
Another question might be, would you be willing to provide a G2 power supply for pentode valves? This would need to be a (not too demanding) current source bypassed to cathode (or maybe signal ground?). CCS only needs to be large compared to reciprocal of Gm, maybe just a resistor. Transmitting pentodes will never have a G2 voltage rating large enough for your use, so cannot be triode connected. The advantage of pentodes is that the cool kids ignore them, so excellent candidates, like the 4E27 family, are "a drug on the market", so affordable.
All good fortune,
Chris
Type 4E27 is cheap and available, and reasonable-ish on heating power (37.5W each), but, as an Eimac, doesn't have always-on gettering. Part of the price to be paid today for the beautiful technology of the Cold War is our effort to awaken these sleepers. Just exploring this myself, but the sure bet is to plan on a "restoration rig", which could possibly be the amplifier itself, if planned for. The gig is to get the anodes hot enough to getter the envelope, so needs a filament supply, a grid current meter (and bias supply) and a variable B+. It's a real-time project, but probably won't take even an hour. Maybe - don't know yet. Might not even be necessary - don't know yet.
They'll want a G2 voltage in the 600 - 700 VDC range, above cathode, so possible but not trivial. I'd suspect that anything else that can do the job would be similar.
The mystery of how you're supplying current to these valves remains a mystery. I, for one, am staying tuned.
Always the best,
Chris
They'll want a G2 voltage in the 600 - 700 VDC range, above cathode, so possible but not trivial. I'd suspect that anything else that can do the job would be similar.
The mystery of how you're supplying current to these valves remains a mystery. I, for one, am staying tuned.
Always the best,
Chris
Jan
since you already have adjustable up to 4,4KV HV DC source I propose you to made one simple test jig just to record specific basic results whatever which type of tube you want to use , but allways triode strapped with all grids and beam plates electrodes grounded , and before you further develop the real amp circuit of course , by using this simple test circuit you can watch what Ik and Vk you get when you manualy adjust both Va and Rk , also in this way you can determine max. anode disipation.
ps ,filament heater supply allways have to be floating type , let`s say supplied from some isolation transformer , just to suppres arcing betwen cathode and filament in case you testing those TV beam pentode tubes .
since you already have adjustable up to 4,4KV HV DC source I propose you to made one simple test jig just to record specific basic results whatever which type of tube you want to use , but allways triode strapped with all grids and beam plates electrodes grounded , and before you further develop the real amp circuit of course , by using this simple test circuit you can watch what Ik and Vk you get when you manualy adjust both Va and Rk , also in this way you can determine max. anode disipation.
ps ,filament heater supply allways have to be floating type , let`s say supplied from some isolation transformer , just to suppres arcing betwen cathode and filament in case you testing those TV beam pentode tubes .
Attachments
Jan
with proposed test jig you can test those tetrodes or pentode tubes including GMI-11 tetrode tube in both ways , with g2 connected to ground line or with g2 connected to cathode , but with g1 control grid allways tied to ground line , it is all depends from final test results , and from resulting tube parameters which is the best suited for your solid state cathode driver circuit , and of course also depends from primary task to get the best basic or open loop overall linearity ,
btw , think in case that you get cathode voltage in range of 200-400DC than that bipolar driver power transistor can be the one from those again TV or even better CRT-PC-monitors horizontal output stage ?, like BU508 ,BU208 , or simmilar HQ- HV transistors .
with proposed test jig you can test those tetrodes or pentode tubes including GMI-11 tetrode tube in both ways , with g2 connected to ground line or with g2 connected to cathode , but with g1 control grid allways tied to ground line , it is all depends from final test results , and from resulting tube parameters which is the best suited for your solid state cathode driver circuit , and of course also depends from primary task to get the best basic or open loop overall linearity ,
btw , think in case that you get cathode voltage in range of 200-400DC than that bipolar driver power transistor can be the one from those again TV or even better CRT-PC-monitors horizontal output stage ?, like BU508 ,BU208 , or simmilar HQ- HV transistors .