>.....
>1. Can the resistance of a carborundum type noninductive
>resistor be altered by shortening its length and still
>be useable?
yes
> I have only one now and don't want to damage it.
>
If it has too much R, it can be cut down with carbide saw.
>2. With a 8169 grid driven tetrode, can I have too much
>C from each side of the filament to ground?
Yes. Large capacitors tend to have more internal L. A good bypass
should have minimal L. For bypassing each side of the filament of a
large tetrode, I use multiple HV disc-ceramic capacitors of three
different values, all in parallel. I like to limit the peak current in
each cap. to 1A, so for an 8171, it takes about a dozen bypass caps for
each side of the filament. . Total Xc should be less than 1-ohm for each
side of the filament
> If so, what would be too much?
>
It takes a dipper to find out. Clamp the cap. in a copper-jawed vice and
measure the self resonance freq. If resonance is within the operating
range, you need a capacitor with less capacitance.
The goal is not to operate any bypass cap. above its resonant freq.
Above resonance a capacitor looks like an inductor. In other words,
bigger is not always better.
.
cheers, Bruce
- Rich..., 805.386.3734, www.vcnet.com/measures.
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