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Re: Why do I have DC on my cathode-biased input tube's grid?

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Chris O

(A)

In Reply to: Why do I have DC on my cathode-biased input tube's grid? posted by Alexo on April 27, 2007 at 08:39:54:

What voltage do you have on the tubes cathode? Or in other words, what is your tube's plate draw?
Have you tried replacing the 12AX7 with another sample?
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Re: Why do I have DC on my cathode-biased input tube's grid? - Alexo 11:05:43 04/27/07 (1)
With the 620 ohm resistor:
Rail voltage: 163
Plate Voltage: -.6 (think I put -.4 in my other post, it was -.6)
Cathode: .4 volts
With 1K8:
Rail: 178 (rose due to an unrelated circuit change)
Grid: -.17
Cathode: 1.06
- Gah! Errors! See the corrections here: - Alexo 11:07:21 04/27/07 (0)
  With the 620 ohm resistor:
  Rail voltage: 163
  Plate Voltage: 92
  Grid Voltage: -.6 (think I put -.4 in my other post, it was -.6)
  Cathode: .4 volts
  With 1K8:
  Rail: 178 (rose due to an unrelated circuit change)
  Plate: 106
  Grid: -.17
  Cathode: 1.06
Re: Why do I have DC on my cathode-biased input tube's grid? - danlaudionut 11:04:44 04/27/07 (0)
Chris
If you run the numbers you'll get .625mA.
I agree the tube is suspect.
DanL

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