[Boatanchors] FW: [Johnson] Valiant Troubleshooting Question

[Rob Atkinson]

I've never owned a Valiant and don't know how the space is but if
possible I'd replace those mica caps with two small RF HEC doorknobs
for ~330 pF and 150 pF.  Try to find class 2 dielectric temperature
and RF current figures at 1 Mhz before buying.  RF parts has that kind
of data with their HEC doorknobs.   You might be okay with disk
ceramic caps but on 160 m. AM they can drift.

73
Rob
K5UJ



> A known failure point in the Valiants is the supplementary fixed loading
> capacitors.  They are sandwiched silver mica caps that are encased in wax.
> They are known to fail, presumably with shorts or high leakage.  Since they
> are in high RF current service, ordinary mica caps will not perform
> correctly, so be careful in picking replacements.
>
> There two sets of four caps in series parallel -
> C39A, B, C, and D are each 330 pF form a total capacitance of 330 pF and are
> used in only some band positions.
>
> C 38A, B, C and D, each 150 pF for a total capacitance of 150 pF are engaged
> on only one band position.
>