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

[2@vc.net (measures)]

>
>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.
>
One does not have to remember anything if one puts the glitch R in the 
positive HV lead.  

>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. 

Limiting the V-drop across the glitch R to 1.5v will hardly allow it to 
limit current. 

> If an arc inside the tube penetrates through the grid to the cathode, 

I have autopsied dozens of tubes.  I have never found a penetrated grid.  
  

>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,   ...

 It can not be the same current if the Glitch R drop is limited to 1.5v 
by the glitch diode.  
---------
In "The Almost Perfect Amplifier"  (*QST*/January, 1994), I recommended 
using a rheostat to adjust filament V.  During the grate parasitics 
debate, at least five members of the Rauchian camp argued long and hard 
that a rheostat can not be used to control filament V.  

end

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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