ORIGINAL MESSAGE: (may be snipped)
On Thu, 10 Oct 2013 03:15:25 -0700, Jim wrote:
> The grid meter wont be damaged at all. Even with rvs
>connected diodes across the grid meter, the predominant fault path is from
>chassis through
>the 4-6 x paralleled diodes, then directly to the B- of the filter caps.
REPLY:
For what seems like the millionth time, placing diodes directly across the
grid meter will not protect it. You must place a resistor in series with the
meter and connected the diodes across the meter + resistor combination.
The diodes don't conduct until the voltage across them reaches about .6
volts. If they are connected directly across the meter with no resistor, the
meter will be destroyed long before the .6 volts is reached.
Choose the value of the resistor so that the .6 volt figure is reached at
about 110% of full scale. Don't forget to include the meter resistance in
the calculation.
This also applies to the plate meter or any low-resistance current meter,
which nearly all of them are.
73, Bill W6WRT
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