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On Sun, 4 Dec 2016 06:13:07 -0600, you wrote:
>Ok but some of us are about on our last go-round. What do we do for our
>thousands of SB 2nn series Heath amps??
>73
>K5DAM
REPLY:
If it were my SB 2xx amp I would replace the 3-500(s) with a single
8877. It is a smaller tube so it should fit OK, and a single 8877 has
more power capability than a pair of 3-500's and needs only about half
the drive for the same output. The filament voltage is the same and
filament current is less, so no change is needed there.
I have never actually done this so there might be a gotcha I'm not
aware of and you would need to proceed carefully, but if successful
you would have a much better amp. More headroom, better reliability,
less drive and in most cases an 8877 does not need a parasitic
suppressor. My homebrew 8877 amp does not have one and is perfectly
stable on all bands. I have seen numerous other 8877 designs that do
not have one either.
Making a change like this is not for the inexperienced and if you are
unsure about it, you should probably find an Elmer to help you.
73, Bill W6WRT
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