Hi Folks:
Several years ago I re-drew the complete schematic of the Heathkit
SB-220 in two versions, two (2) 8-1/2" X 11" pages and one since 11"
X 14" page, and posted the schematics several different locations for
all the be able to access once their venerable old, WORN, schematics
finally wore out, or had so many notes on them that the were no longer usable.
I also asked for folks to write with any corrections to the re-drawn images.
Over the years, I received several minor corrections, which were made
to the schematics I have posted to my web site (www.n0ss.net)... FREE
for the downloading.
I recently received a note from George, W0MKZ, noting that the pinout
of the SB-220 T-R relay in HIS schematic was somewhat reversed from
that which I showed in my re-draw. George also noted that he thought
he recalled reading (somewhere) that Heath has, at some time, swapped
the (outer) T-R relay pinouts back 'n forth.
I'd like to ensure that the pinouts for the T-R relay I show in my
schematics is correct, and if not, FIX IT. I'd also like to add a
footnote if Heath really did swap the pin annotations somewhere down
the line, just to help those who might have a slightly different schematic.
My schematics currently show the T-R relay pinouts (as viewed from
left to right on the schematic) as:
6,9,3 4,7,1 5,8,2
While George's pinouts (1969 SB-220 manual) are:
5,8,2 4,7,1 6,9,3
If anyone's willing to do so, I'd appreciate it if you could please
consult your SB-220 manual(s) and drop me a note as to which pinout
scenario YOUR manual shows. Please also note the publication date of
YOUR manual.
I'll take as many responses as I can get... it only takes ONE
response which matches the pinout I used to get me to trigger a
footnote, but I'd also like to try to get a bit of a handle on how
many different pinouts might have been used.
If no one can confirm the pinout I'm currently using, I'll just take
it that I had a bad day and need to correct my annotation error.
Thanks for any assistance you can lend. It's nice having access to a
pristine SB-220 schematic, but only if it's ACCURATE.
And no, I do not have an SB-220, so I can no longer consult my manual.
73,
Tom Hammond N0SS
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