In Reply to: Well that was quick....... posted by vinnie2 on October 11, 2014 at 13:20:19:
Vinnie,
Please look at this excerpt from my FAQ post on the Tube Asylum:
"Keep one last thing in mind - often you see a voltage "spec" on a schematic at the control grid of a tube. DO NOT TRY TO SET THE VOLTAGE AT THE GRID TO THAT SPEC! The negative voltage at the tube grid should be whatever value is required to set the tube's cathode current to spec. If the tube is passing the correct amount of current and the voltage at the grid is -20 volts then the hell with the "spec" of -22.5 volts or whatever it is. Making the grid voltage more negative with respect to the tube's cathode is the equivalent of stepping down harder on a garden hose to restrict the flow of water. And if you let up the pressure on the hose and more water flows - that's the same thing that happens if the tube grid is less negative!!"
Variance from tube to tube is why this all occurs. Not every tube passes the same amount of current even if all else in the circuit is identical.
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Follow Ups
- RE: Well that was quick....... - Jim McShane 14:04:34 10/11/14 (10)
- RE: Well that was quick....... - vinnie2 17:24:17 10/11/14 (6)
- RE: Well that was quick....... - Jim McShane 19:47:41 10/11/14 (5)
- RE: Well that was quick....... - vinnie2 04:14:53 10/12/14 (4)
- RE: Well that was quick....... - Jim McShane 17:32:46 10/13/14 (3)
- RE: Well that was quick....... - vinnie2 18:44:32 10/13/14 (2)
- RE: Well that was quick....... - Jim McShane 10:23:06 10/14/14 (1)
- RE: Well that was quick....... - vinnie2 14:29:58 10/14/14 (0)
- RE: Well that was quick....... - vinnie2 17:18:49 10/11/14 (2)
- RE: Well that was quick....... - Jim McShane 19:39:05 10/11/14 (1)
- RE: Well that was quick....... - vinnie2 05:54:38 10/12/14 (0)