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

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

Andy Cook, G4PIQ 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.
>
You're right, it doesn't necessarily. 

There are just two things to take care of, if the glitch resistor is in
the negative lead: 

1. To be sure that the resistor is the *only* path back to the HV-minus
point (and is not bypassed by the meter protection diodes). This
requires some thought and drawing-out the simplified DC circuit to make
sure it's correct.

2. To be sure that the insulation around the negative end of the
capacitor stack will withstand voltages spiking to MINUS HV. This also
applies to the negative end of the glitch resistor and any connecting
wiring.


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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