>I was looking through the Amps archives and I noticed some comments about
>damage to the 160-meter padding capacitor bandswitch contact due to Heath not
>providing a
>corona washer.
Corona at 2800pV on a 5000pV capable bandswitch?
> Sure enough, my SB-1000 has a burned bandswitch contact in
>this place. I'd put off fixing it and attributed it to the former owner's
>hot-switching...but maybe that isn't what happened after all.
The SB-1000 is essentially an AL-80, and whose replacement parts happily
fit.
>Could someone please educate me with regard to this? What causes this
>problem, and what kind of washer needs to be put where to prevent it?
Replacing the
>contact is going to be annoying (I really don't want to replace the whole
switch) and
>I only want to do it once!
Open160m tune padder switch contacts tend to arc during intermittent vhf
regeneration. at roughly 155MHz. If you couple a dipmeter to either
side of the hv dc blocking cap. you just might see a sharp dip near this
freq. You can find some photos of parasite arced bandswitches at:
www.vcnet.com/measures
- It is my opinion, based on conversations with the owners, that none of
these bandswitches were ruined by "corona", "operator error, bad
antennas, or by cheap coax". {Charles Thomas Rauch, Jun., W8JI} . The
likely fix is to replace the burned contact, or to replace the wafer if
the ceramic is blackened with metal vapour condensation, and to decrease
the vhf Q of said vhf-resonant circuit.
- later, Vic
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
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