** This a common problem, especially among contestors, where the
high-ESR of the compact flash-type C that is used causes heat-buildup
which stresses the solder seals and eventually breaks them. If I were
looking to replace a leaky oil-filled filter C in a 77, I would consider
replacing it with a bank of the new, compact Matsushita/Panasonic 105ºC,
high-ripple-I 450wvdc electrolytics. Sure, this modification will
totally destroy the cosmetic value of the amplifier to the
appearance-minded, but the 77's reliability would be improved. On the
other hand, this would be undesirable to those who like surprises during
contesting.
- Another worthwhile 77 mod is replacing the 80m and 160m tank-padder
doorknob caps for with units that are rated for tuned-circuit duty
instead of bypass duty. This will stop the tank heating and drifting
problem on 80 and 160. Yet another mod to consider is decreasing the Q
of the VHF-suppressor. Although this will result in a 2% or so power
loss at 29MHz, the VHF-gain of the 8877 will be reduced, which just might
make it less squirrely at the VHF anode-resonance. (measure with a
dipmeter at the DC-blocking C)
-- Note -- I have autopsied several 8877s from Alpha 77s which died from
gold-sputtering off of the grid, a phenomenon that Eimac's 8877
design-team reportedly concluded was caused by an "oscillation
condition".
>Noticed my origial Filter Cap is starting to leak oil. Is there any
>other place to buy a replacement cap other than Peter Dahl?
>
>Thanks..
>Rich N7TR
>
>N7TR Web Site - Updated 28 Sept
>www.n7tr.com <http://www.n7tr.com>
>
>N7TR DX-Cluster
> <telnet://dxc.n7tr.com>
>
>
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