On Nov 1, 2006, at 5:59 PM, zerobeat40 wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
It can't be Rauch because he knows that the grid has to be positive
with respect to the cathode in order for grid-current to flow.
Sounds like someone needs to review his basic tube theory.
Specifically, look up "contact potential bias".
As I recall, the problem is that "Z" previously stated that, according to the characteristic curves, a 3-500Z(?) flows __mA of grid current when the grid-cathode potential is negative __V. According to the characteristic curves, grid current does not flow until the grid is positive.
Free, unsolicited advice: when you step in it, you can not succeed in hiding it from others - even if you are a discussion group "Administrator" who censors posts that discuss his misstatements.
Now, for the experiment.
Lay tube on bench. Any tube, as long as it works. Apply specified
filament/heater current. Place a high-Z voltmeter between the
cathode/fil and the control grid. Once the cathode warms up, what do
you read? Is the grid negative W.R.T. to cathode, or positive? Given
that the voltmeter has finite resistance, would you say that the grid
current is zero, or non-zero?
Connect a 100kohm resistor between grid and cathode. Measure the
potential difference between grid and cathode. Given that this
voltage is non-zero, is there grid current? What is the polarity of
the voltage?
The experiment is more dramatic with a transmitting tube. I don't
recall what the values will be for a 3-500Z, but I just ran through
some 4CX250Bs...typ voltage developed in the experiment is control
grid negative to cathode by 15-30 volts, with grid current flowing.
The only places where like charges attract are West Hollywood, Palm Springs, the Gay Bay (SF) et cetera.
Let us know the results.
he has a mouse in his pocket?
cheerz
...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
