> Uhhhh Tom, your mis-quoting me again. I said the grid
> would not go over 0 Vdc if connected to ground. I also
> said it would stay negative or at 0 Vdc if those ions
> flying around in a gassy tube were happening. A tube can
> have the ions without an arc. Also, which direction does
> an arc occur, from the anode to the grid, or from the grid
> to the anode, or which way is the electrons in the arc
> flowing?
Will,
Early on you said contact bias and grid leak bias were the
same, they are not. You also said when the grid was floated
during a fuse or resistor blow, it would go negative. It
does not in the case of a power grid tube. I'm sure most
people remember that, and the archive clearly show it.
Now it appears, running out of escape avenues, you want the
grid grounded at all times.
Since that is what I said all along, that the grod belongs
grounded, it appears you finally agree and see the point.
>> We
>>need somehow to bring the grid up positive to anode
>>potential to reduce current and quench the arc.
>
> Or is it bringing down the anode potential to match the
> grid? Do you have a voltage drop with current rise?
We now agree again. You now appear to see the merit of a HV
fuse and current limiting system. Everyone agreed on that
all along, and now you are on the team.
> In order for
>>the grid to go to anode potential, the grid has to move
>>significantly positive with respect to the chassis (and
>>cathode).
>
> Remember, the grid is still connected to ground at this
> point.
Yes, because NOW you have removed the silly poorly
engineered grid fuses. We again agree.
> Once the grid is even remotely far enough positive
>>to reduce the arc, it is so far positive it almost
>>certainly
>>has exceeded the breakdown voltage of the grid to the
>>cathode. Now we have a grid, arcing to an anode, that is
>>also arcing to the cathode
>
>
> In what direction does the cathode to anode arc occur or
> which way is the electrons in the arc flowing?
Electrons normally move from cathode to anode Will.
>>The entire idea of pulling the grid off ground to reduce
>>grid-to-anode fault current is, quite frankly, very poor
>>design.
>
>
> I couldn't say, I've never tried it.
Then why did you waste 50 posts arguing with me and others
about it, only to finally agree it is a bad idea?
> Ehhh, there you go again Tom. Nowhere did I ever say
> arcing was less likely if the grid was fused. Matter of
> fact, I said it wouldn't help the tube at all because the
> tube was bad, it was gassy. The only thing it might help
> is saving the B+ supply from ruin. Evidently, you don't
> read all the threads, or have one helluva time
> understanding them.
1.) I understand what most people say very well Will. The
only time I have a hard time understanding someone's
position is if the change it constantly.
2.) I can't say the same for other people. As an example
look just above. I very clearly said, "The entire idea of
pulling the grid off ground to reduce
grid-to-anode fault current is, quite frankly, very poor
design."
3.) You will not find the words "arcing is less likely" in
my text above Will, so I certainly don't know how you came
up with that.
4.) Your statement above, "Matter of fact, I said it
wouldn't help the tube at all because the tube was bad, it
was gassy ", is totally incorrect. Anyone inside the
industry or using large power grid tubes knows that
occasional hard faults are not unusual. Dozens of people
have repeated that here on this thread. When a tube arcs, it
does NOT mean the tube is bad. This is why it is important
to not cause more damage than we need to during a hard
fault.
Are we done Will, now that we both agree fusing the grid
does nothing good?
73 Tom
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