[AMRadio] SB-221 to SB-220 Conversion

[Donald Sanders]

Lee I didn't see another reply so here goes. The SB221 is the same as the SB200. 
The band switch has a stop to be removed to allow the switch to go to the next 
position for ten meters. In the input there is a filter to prevent 10 meter 
exitation that has to be removed. You may have to add the input coil and 
capacitor. I can look at my SB200 and tell you what they are. Heath sold a kit 
to add 10 meters.
BTW Harbach Electronics sells the bandswitch wafer in ceramic for the final 
bandswitcch for $35 in case you should need one. I ordered the PS kit and the 
soft start and am waiting to receive them now. My SB200 has the original parts 
from the 60's so it's time to upgrade the PS, though it still puts out 600 watts 
with a bit more HV drop than I like. Those are old electrolytics in the PS. It 
is amazing that the old CETRON 572Bs are still working well. Rugged tubes.
Don W4BWS/HC4   




________________________________
From: LEE BAHR <pulsarxp at embarqmail.com>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Sun, October 3, 2010 1:19:31 AM
Subject: [AMRadio] SB-221 to SB-220 Conversion

Can the conversion of a SB-221 be made to a SB-220 from readably available 
parts?  I am in the market for an amp for my club W5DRC.  I was and still 
might be looking for a SB-200 that looks clean in which I could install the 
Harbach updates and wind up with a nice amp.  We want 10 meters on the amp. 
That was our initial plan.  However, a friend of mine just contacted me and 
said he has a nice SB-221 he would sell me.  But, the amp doesn't have 10 
meters on it.

I think, to make the conversion I would need an input coil, a changed out 
input wafer switch and a tank coil wafer switch and then tap the 20/15 meter 
coil .  I can't find anything on the internet how it actually would be done 
or if it can easily be done.  I don't find anything in the FILE section 
either of this group.  If I can't fairly easily put 10 meters on the SB-221, 
I need to tell my friend I am going to pass and look for another amp.  I see 
Harbach sells a wafer that would work for adding 10 meters to the tank 
circuit.  I would think the input coil would not be too hard to duplicate, 
but the input wafer may be hard to find or very costly making the conversion 
not worth while.

Does anyone on here know what can be done and procurred for the conversion? 
Frankly, I was suprised to not be able to find anything about doing this on 
the internet.  I do realize Heath once had a conversion kit available, but 
my chances of finding one of those would be slim to zero these days.

One last thing, are the Chinese 572B tubes sold with the Taylor name on them 
from RF Parts any good these days?  Those tubes scare me if we wind up with 
a SB-200.  (I know a couple years ago the Chinese 572Bs were bad news and 
the Svetlana tubes were really made for audio and had smaller plates on them 
so they were not really good either.  Plus the fact the 572Bs in a Heath amp 
lie on their side causing "sag" with some of the Chinese tubes).

Can anyone help me out regarding all this?  Thanks for the consideration.

Lee, w0vt


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