>
>Picking up on one of Rich's remarks:
>
>>Henry's glitch-R in the neg. HV
>>lead is a mistake. A glitch R should be added to the pos. HV circuit.
>
>It doesn't really matter which end of the HV circuit the glitch resistor
>and HV fuse are - unless the designer thinks that putting them in the
>negative return rail requires less insulation. In fact it requires
>*more* insulation, because a "crowbar" short from HV+ to chassis will
>tend to push the return rail down to *minus* the normal HV.
>To avoid breakdown, the negative rail and the negative end of the
>capacitor stack therefore need to be insulated to the same standard as
>the positive end.
>
? The sticky wicket with putting the glitch-R in the neg. hv circuitry
is that the filament transformer/cathode circuitry must be insulated for
several kV. However, allowing the cathode to rise to several neg. kV
during a HV+ short to chassis is likely to cause an arc to the
grounded-grid. Thus, it is my opinion that it matters which end of the
HV circuit the glitch-R is in.
- cheers, Ian
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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