John,
Very nice work! Especially how you took the mods out one by one. I
thought the shielded tube socket was a horrible idea for cooling, but
someone obviously thought shielding was more important. It goes to
show that cheap ol' Heapkit stuff was pretty decent.
The SB220 is my favorite SSB amp. I always liked the simplicity, sort
of the VW of power amplifiers, but yet it worked well. My other
favorite Heath is the KL1 Chippewa from 1960, pair of 4-400A's with a
enclosed blower on the back.
My 220 has most of the standard mods, like bias mode
switch(standby/op), step start, better rectifiers, Measures
suppressors, better ant relays, improved input matching. I think I
picked it up 12 years ago for $250, thats about 20 cents/watt for
typical 1200 watt linear output on 20 meters.
73
John
K5PRO
>
>Message: 8
>Date: Fri, 10 Mar 2006 13:34:03 -0800 (PST)
>From: <johna8119-amps@yahoo.com>
>Subject: [Amps] SB-220 Unmodification
>To: amps@contesting.com
>Message-ID: <20060310213403.36463.qmail@web53612.mail.yahoo.com>
>Content-Type: text/plain; charset=iso-8859-1
>
>Some of you may recall that last summer I posted some questions
>about an extensively modified
>Heathkit SB-220 that would not work. I put some pictures, etc. on a web page.
>
>Several of the helpful guys with comments asked that I keep the
>group up to date with the
>progress. I am finally finished with this project, and the web
>pages tell the saga.
>
>If you are interested and have a few minutes, here is the site:
>http://www.geocities.com/w4kv/sb220
>
>You will need broadband, because the pictures are too big for dial-up.
>
>73,
>
>John
>w4kv
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