[AMRadio] 572B's !

[Peter Wittenberg Sr]

Lee, I use large quantities of Svetlana 572B's in my customers Collins 30L-1
Amps. They are good and you should buy them form Frank Krize at:
k5svc at natchez.net.  He is a very honest Ham and if there are ever any
problems he stands behind what he sells.  I try to Avoid any of the Chinese
tubes but in the future those may be the only ones you can find. The
Svetlana tubes are limited stock at Frank's and RF Parts.

-73- Peter K2LRC
www.k2lrc.com

God Bless America!

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of LEE BAHR
Sent: Sunday, October 03, 2010 2:20 AM
To: Discussion of AM Radio in the Amateur Service
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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