>
>On Fri, 10 Oct 97 00:22:28 -0800 Rich Measures <measures@vc.net> writes:
>
>SNIPS
>
... ...
>>IF a 1000pF capacitor bypasses RF from the anode circuit, it seems
>>unlikely that much VHF energy could get past that bypass and invade
>>the glitch resistor.
>
>In the SB-220 that 1000pf bypass cap is highly reactive at VHF.
What is the resonant frequency of this capacitor with a wide copper-foil
short across it?
>It is not
>RF rated. However replacing with a 1000pf disc ceramic with very short
>leads will do the job.
>As I tried to allude to earlier, not all VHF energy flows thru the
>primary RFC path in that amp due to the physical layout.
>
I do not see how. The vhf choke, RFC-2, (or it's replacement, the glitch
R) is some distance from the anode's VHF-resonant circuit. I have never
seen this choke damaged by a VHF parasitic-oscillation - - nor have I
seen a SB-220's main RFC damaged by a parasitic, probably because it has
no resonance around the frequency of parasitic-oscillation - 110MHz.
Rich---
R. L. Measures, 805-386-3734, AG6K
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