Rich has said on a number of occasions, and, I believe, without
contradiction, that it is well worthwhile measuring the value of
parasitic suppressor resistors after a flashover. My question is:-
Do the values change because of long term over heating, which would
possibly show up in surface colour change?
OR
Is there an enormous pulse overload causing the value change? If so, why
is there no apparent visual colour change - or is there? Does it depend
on the resistor type?
If we assume that Rich is correct with the parasitic theory, then it
suggests that the suppressors do get a large power input during the
parasitic oscillation duration. If the change is due to long term
heating merely because of the RF power dissipated from the plate current
flow dividing between the resistor and the shunt inductor, then the
change should be similar to that which would appear from heating the
resistors with DC.
Just to add to the debate, I haven't seen anyone come up with a boiling
point temperature for gold in a vacuum - if it's lower than at
atmospheric pressure, then the arguments about grid temperature take on
a new dimension.
73
Peter G3RZP
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