SB-104A 400Hz CW FILTER QUESTION

[John Farrington]

At 05:46 AM 12/28/2001 <kd5hcl at YAHOO.COM> wrote:

>Just picked up a 400Hz xtal filter for my SB-104A, but
>now I'm scratching my head. The board this goes on is
>missing all the nearby associated components. Was the
>cw filter option actully a kit containing all of these
>other parts?


That's board-E, the "Carrier Generator/Xtal Filter Board".  Heath
put out a separate "CW Filter Accessory Kit" and manual for installing
the 400 Hz CW filter, so it seems they did not feel it necessary to put
the values for all of the I/O parts on the main SB-104 schematics,
including those for the 4 toroid inductors L676, L677, L678, & L679.

The manuals site at bama.sbc.edu doesn't list that filter kit manual,
but maybe someone on the reflector has a copy;  if so, I'd also
appreciate information about the part values.

If you can get the inductor values, and have a dip meter or inductance
meter, you can wind your own with enamelled magnet wire (for guage look
at the wire on the toroids for the SSB filter) on the apropriate
size/frequency-range toroid cores from Amidon:
   http://www.amidoncorp.com

The original cores were potted in a phenolic holders with solder pins,
but if Amidon doesn't have cores with holders you could make some up
or just use silicon rubber.

To look for a copy of the manual, you might ask W7FG Vintage Manuals at
http://www.w7fg.com/

or the SB-104 repair site at
http://www.qsl.net/k5bcq/sb104/sb104.html
  or
http://www.inetport.com/~talen/sb104.html.

There's a message board at  http://members3.boardhost.com/heath32a/
where you could post inquiries.

Perhaps Heathkit Educational Systems at  http://www.heathkit.com/
can still supply an original manual or copy for $20 or so.

If you can't find the Heathkit filter manual, you might try asking
about it at International Radio:
   http://www.qth.com/INRAD/

as they make xtal filters:  they list a 400 Hz CW filter (reference 2702L)
for Heathkits, so they might be able to tell you the values for the various
original input/output components on Board E. I presume they have a manual
for their own kit that they might sell you, but you'd have to ask if their
I/O components for the E-board would be the same as the originals.

73

John  KE5ZB

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