[AMPS] AL-1500, AL-82, AL-1200, QRO???

[Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK)]

Rich wrote:
>
>>
>>Rich wrote
>>> The glitch R needs to be in the positive HV lead.
>>
>>Piece of education needed for me here. The glitch resistor is there to 
>>limit fault current in event of a flash-over. The only source of these big 
>>currents is from the filter capacitor and the only route for the current 
>>back to that cap is via the 25R resistor. So why does the resistor need to 
>>be in the +ve line.
>>
>The typical positive filter cap ckt is insulated for several kV.  
>The negative filter cap/cathode circuitry/fil. transformer CT is not.  

The negative end of the filter cap can easily be insulated to those
standards - you just have to remember to do it.

The cathode circuitry and filament transformer (assuming we're talking
about GG triodes) would not see a spike caused by a direct short or arc
from B+ to grid or chassis - they are protected by the glitch diodes. If
an arc inside the tube penetrates through the grid to the cathode, those
components are not protected any differently by a glitch resistor in the
B+ or the B-minus. As Andy said, it's the same surge current flowing
around the loop, so if we measure everything relative to chassis
potential, it's also the same voltages.


73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.com/g3sek

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