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Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
hey,
i was gonna use these tubes in a vacuum tube tesla coil, but they are pentodes, and i wanna use this circuit so where do i connect the extra grids, so i can use it as a triode?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
1) Connect control and screen together, ground suppresor grid. 2) Build a dedicated supply of a few hudred Volts for the screen (use a limiting resistor in series), put feedback to the control grid and ground suppresor. 3) (Experimental) Ground control and suppresor grids, feedback only to screen.
Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Dr. Kilovolt wrote ...
1) Connect control and screen together, ground suppresor grid. 2) Build a dedicated supply of a few hudred Volts for the screen (use a limiting resistor in series), put feedback to the control grid and ground suppresor. 3) (Experimental) Ground control and suppresor grids, feedback only to screen.
okay. thanks, how do i know which grid is the control grid, which is scree, and which is suppressor? the tube just says grid 1, 2 and 3.
and also, will this tube will work as well as the 811a in the vttc circuit? (its voltage and current ratings are correct)
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
alf wrote ...
Dr. Kilovolt wrote ...
1) Connect control and screen together, ground suppresor grid. 2) Build a dedicated supply of a few hudred Volts for the screen (use a limiting resistor in series), put feedback to the control grid and ground suppresor. 3) (Experimental) Ground control and suppresor grids, feedback only to screen.
okay. thanks, how do i know which grid is the control grid, which is scree, and which is suppressor? the tube just says grid 1, 2 and 3.
and also, will this tube will work as well as the 811a in the vttc circuit? (its voltage and current ratings are correct)
thx. Alf.
The grids are numbered in order away from the cathode.
First is the control grid, or g1 for short, closest to the cathode.
Second is the screen grid, or g2.
Third is the suppressor grid, or g3.
As for the last question, valves work best, and are most reliable, when they are set up using the datasheet values.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
alf wrote ...
ok thanks, so id have to redesign this circuit?
The design ratings for an 813 self-rectifying Class C oscillator are given on page 2 of this datasheet here:
Read down the ratings in the Self-Rectifying Oscillator or Amplifier - Class CMaximum CCS Ratings section, and have a look at the OO footnote flagged on the AC grid no. 2 (RMS) line. I suspect this may be more trouble than you had bargained for.
Someone is bound to suggest strapping g1 and g2 together, but I have no comment to make on that.
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how to use a pentode as a triode?
