>
>measures wrote:
>>>
>>>Wilbert Knol wrote:
>>>>
>>>>
>>>>> With the glitch R in the negative return, the cathode circuitry may be
>>>>> driven to several kV by a B+ to chassis arc.
>>>>
>>>>Good point.
>>>>
>>>>I don't like the idea of most of the HT appearing across the filament
>>>>transformer secondary...
>>>>
>>>Does it?
>>
>>With filament-type cathodes, without glitch (meter protection) diodes, it
>>does.
>>
>>>The current around the loop is the same, regardless of whether
>>>the glitch resistor is connected to the top of the capacitor stack (B+)
>>>or the bottom (B-minus). If we keep chassis potential as the voltage
>>>reference, the only difference in the second case is only that the B-
>>>minus end of the resistor spikes to a high *negative* voltage. The other
>>>end of the resistor should be held close to chassis potential by the
>>>usual meter protection diodes.
>>>
>>When the glitch R is connected to the neg. return, the meter protection
>>diodes limit the voltage drop across the glitch R. This prevents the
>>glitch R from doing its job of limiting current.
>>
>>Thus, when the hot end of a B- glitch resistor is held close to chassis
>>potential, the meter protection diodes limit the voltage across the
>>resistor to a couple of volts. Thus, virtually no current limiting is
>>provided.
>>
>
>You're absolutely right, it won't limit current if you put it there...
>but that wasn't where I meant.
>
>Referring to "Figure 2" on your web site, leave the meters and diodes
>exactly where they are.
ok
>Move the capacitor stack, divider resistors and
>rectifiers away to the left to make a separate group of components.
ok
>Connect a single wire between those two groups of components - that is
>the B-minus rail.
>
we are in the subway?
>Now cut that wire, and insert the glitch resistor.
As I see it, the glitch diodes are going to limit the potential across
the glitch R, Ian.
end
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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