re: Heathkit SB-201 tuned input
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The input tuned circuit LC part values of the SB-201 with
"the filter" are obviously different vs the "original SB-200
input circuit values.
-
Removing the filter network changes the remaining
composite input circuit values big time. The resultant
input values less the filter don't work very well at all.
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The fix would be to copy the SB-200 circuit and input
circuit values into the SB-201.
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skipp
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--------- Forwarded message ----------
From: "Mike Baker" <k7ddmjb@qwest.net>
Hello again.
Well, this time I started a project that is getting more complex as
time
progresses.
I offered to service and update a friends Heath SB201 amp. Put in the
Harbaugh soft start, new fan, new power supply filter board, glitch
resistor, new plate choke and new tube sockets.(the old ones were so bad
that one of the tubes had dropped down and shorted the plate connection
to
the plate choke!) Piss poor sockets. Now have new porcelain/ceramic
sockets with clip type connections and the tubes stay where they belong.
(What a pain opening up the socket holes in the chassis with a nibbler
and a
half round file, but it looks nice now.)
In my infinite wisdom I decided to remove the unnecessary filter unit
in
the input circuit as I needed the room for the new sockets anyway. Well,
when I got it all together and tested it out, BAD match to the exciter on
all bands and it won't tune out by adjusting the slugs. So, drag out the
SB200 manual and compare the circuits. All but the 40 meter input coil
are
the same part number. Different cap values and in the case of 15M, no
cap
at all just a coil. So, now here is the $64,000 question.
Do I just duplicate the values that the SB200 uses and retune or is
there a better method? Anyone done this before and have a better fix?
Is
the Q of the input circuit from the SB200 too low and it will look bad to
a
solid state exciter? I am open to suggestions. It looks like either
way, I
have to work on the input network but I would like to not have to do a
total
rework if I don't have too.
So, what say you group? Suggestions???
Thanks in advance for the help......
Mike Baker K7DD
k7ddmjb@qwest.net
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