[Amps] arc to grid basket TSPA

[R L Measures]

On Jul 27, 2006, at 10:16 AM, John T. M. Lyles wrote:

> The anode at the top may be a flat surface,

Not in the ones I've autopsied.

> at the 'dead head'
> region, like the inside of a metal can. At the bottom of the tube,
> there are edges of the anode and the fil/grid connections may have
> other attachments and sharp edges (like a getter assembly on
> filament). I see no reason to question why it wouldn't arc here just
> as easily as up at the top where the anode/grid may have smoother
> contours.

Then we agree that an arc would most likely take place at the top of  
the grid support cone, and not at its bottom as was claimed earlier.
>
> 73
> john K5PRO
>
>
>> Message: 8
>> Date: Wed, 26 Jul 2006 14:08:44 -0700
>> From: R L Measures <r at somis.org>
>> Subject: Re: [Amps] flash arcs
>> To: "Tom W8JI" <w8ji at w8ji.com>
>> Cc: amps at contesting.com
>> Message-ID: <499C6EB0-B570-43FE-88F2-745E616FBCDA at somis.org>
>> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>>
>>
>> On Jul 26, 2006, at 4:12 AM, Tom W8JI wrote:
>>
>>>
>>>>  According to Gossling's paper in the Journal of the IEE
>>>>  (which means it was certainly peer reviewed!), flash arcs
>>>>  is slightly affected by residual gas: the 'clean up'
>>>>  effect of the arc can lower the flashing voltage. He
>>>>  recommends series resistance in the anode supply (now
>>>>  where have we seen that recommended!) but says that it
>>>>  isn't generally pracitcable with valves over 10kW. He
>>>>  comments that the 'most general visible after effect is
>>>>  widespread tree like markings on the grid and filament
>>>>  supports. The fine wires in the active part of the grid
>>>>  are, however, never damaged.'
>>>
>>>  That's exactly the type of damage I have seen. As I posted
>>>  earlier, 3-500z's generally mark the grid support cone at
>>>  the bottom with very fine lines.
>>
>> Since the top of the grid cone is closer to the anode than the bottom
>> is, why wouldn't the arc take place at the shorter distance?
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R L MEASURES, AG6K. 805-386-3734
r at somis.org