[Amps] grid fuses

[Joe Subich, W4TV]

Will writes: 

> Joe, your not compairing apples to apples here. Your 
> compairing a vary large capacitor to a piece of wire about a 
> foot long (if that) when its straightened out. I've never 
> seen the grid in a tube charge up by setting on the shelf. 
> Also, the re-charging of the large capacitor is caused by 
> something else all together different than what's in question.

You're the one who raised the capacitor issue: 

>> That would be like a capacitor charging up with only 
>> one lead connected to a power supply, and the other lead left 
>> un-connected. It can do it before the fuse blows, but not 
>> afterwards, there's just no path for it to work. 

The grid can and will become positive in the presence of an 
electrode stream and voltages on the other electrodes.  A screen 
will certainly go to full anode potential and destroy the tube 
if disconnected with B+ applied.  If it is hot (from either 
excess grid current, electron bombardment or anode to grid arc) 
a control grid will certainly climb high enough that it can arc 
to the cathode or filament.  These are totally different than a 
tube setting on the shelf or setting in circuit without filament 
power or B+ applied. 

73, 

   ... Joe, W4TV