[Amps] Need some info from the SB-220 schematic, please!

[Gudguyham at aol.com]

Tom, Between the SB-220 amps I have owned and worked on for repair, the  
number is staggering.  I can tell you with certainty that many of the  Sb-220's I 
have seen have had their relays wired 2 different ways.  It  really doesn't 
make much difference electrically since the difference is in  which sets of the 
3 poles on the relay does the antenna switching.  Either  way it works.  I 
often wondered why I have seen the 2 distinct ways of  wiring the relay.  I 
thought perhaps some people just "did their own thing"  with that, but now it would 
make sense that at some time Heath changed the  assembly manual from one way 
to the other and therefore the field  difference.  Most likely there was a 
change but I don't know when it  occurred.  I thought that my experience with 
seeing so many of these amps  and noticing that fact would support the idea that 
a change was made in the  wiring  at some point.  On another note, since I 
have seen SO MANY  SB-220 amps in the past 40 years as a ham, I can tell you 
again with certainty  that about 7 out of 10 SB-220 amps out there have one or 
more burnt band switch  contacts.  JUST BECAUSE THE AMP "WORKS" DOES NOT MEAN IT 
DOES NOT HAVE A  BAD CONTACT OR MORE.  Since the band switch contacts are 
redundant, a set  of contacts can be absolutely toasted and the amp could still 
work on 15 or 10  meters (usually the ones that are toasted).  I'd say if you 
bought a used  SB-220 you have a 30% chance that the band switch is 100% AOK.  
Not good  odds.  It is nearly impossible to check the inside set of contacts on 
the  band switch with the switch installed  in the amp.  The outer contacts  
can be seen with a flash light and an inspection mirror.  Fortunately the  
outer contact seem to go first and can be seen on close inspection, but  
sometimes not.  If a fussy buyer of a used SB-220 was to insist that the  band switch 
be 100%, there would be a bargain basement price on many of  them.  But often 
since they do still work they are taken for regular sale  price.  Off the soap 
box.  73 Lou