Boosted Triode mode?

[Jeb-D.]

http://www.edn.com/article/CA302240.html

Anyone tried this? Looks interesting, but you you would need more iron on the amplifier

 

[Geek]

Hi,

Here's some more boosted triode results. No need for more iron and done heretical

http://geek.scorpiorising.ca/GeeK_ZonE/index.php?topic=1686.msg18638#msg18638

Cheers!

 

[Tubelab_com]

When I first saw the article in EDN I was skeptical, so I tried it. The result? A fried 6L6GC. The author of the article "built" the circuit in a simulator. The simulator may not "see" the glowing screen grid. See post # 18 in this thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=96649&highlight=

And:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=13414&highlight=

And:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=13806&highlight=

I believe that Geeks "boosted triode" is a different design, similar to what I called "dual drive" where the screen and control grids are both driven (at different DC potentials). It works, but the results are dependent on the type of output tube.

 

[kodabmx]

If the screen was glowing I suspect you hooked up the 100V supply backwards. The negative end of the supply should connect to the screen making it 100V negative in respect to the plate. Otherwise it would be the most positive element and quickly burn out.

 

[kodabmx]

Indeed I misread the schematic. Please ignore previous message

 

[Tubelab_com]

The negative end of the supply should connect to the screen making it 100V negative in respect to the plate. Otherwise it would be the most positive element and quickly burn out.

Yes, it will. Been there, fried that!

If the screen was glowing I suspect you hooked up the 100V supply backwards.

The author of the article is the one who got it backwards. It's is fairly common for a rookie engineer who may have been an excellent student in college, but has limited practical experience to "discover" something new and ground breaking in a simulator, but hasn't the knowledge or experience to know that it violates some parameter necessary for success. Sometimes its the laws of physics, other times it is a parameter (like screen dissipation) that isn't even coded in most simulations. LT spice won't even flag plate dissipation since there are no dissipation or voltage specs in the models. Put 2 KV into a 6L6GC, and the simulator will accept it without a warning.

If the simulator tells you that something will not work, chances are it's right. If it tells you something will work, it might. You really won't know until you build it.....that was my job for 20+ years, building and debugging the output of the calculate and simulate breed of engineer.

One of my many tasks in my 41 year engineering career at Motorola was training rookie engineers. Soldering, especially SMD stuff isn't taught in college. Some schools offer little hands on bench experience, especially with state of the art test equipment. No, you can't key a 100 watt transmitter directly into that $30K spectrum analyzer.