[Heathkit] SB-220 Restoration Initiative

[Dennis Younker NE6I]

Hi Jack,

Surprised no one has responded yet but there is a lot of info the web if you
do a search. My own SB-220 is stock except for some recent repairs (blown
capacitor and other fun documented here:
http://forums.qrz.com/showthread.php?454192-SB-220-C4-Overheating/page2 ,
and the Harbach soft key interface (required to interface to modern rigs).
Still going strong after all these years. And frankly, I have never babied
it. So that's a statement on its hardiness.

--Dennis NE6I

-----Original Message-----
From: Heathkit [mailto:heathkit-bounces at mailman.qth.net] On Behalf Of jack m
Sent: Saturday, December 13, 2014 8:30 PM
To: heathkit at mailman.qth.net
Subject: [Heathkit] SB-220 Restoration Initiative

I recently acquired a "stock" (unmolested/unmodified)  supposedly early
production SB-220 amplifier which I plan to disassemble, clean up and
restore for my personal collection and operation with my paired SB-301/401.
 
I have been advised by others that there are several key modifications that
should be performed to ensure reliability and reduce the chances for
expensive damage in the event of certain tube or component failures.  Grid
resistors and different plate cap chokes have been mentioned, as well as
bi-directional meter diodes.  So far, I don't have any details, and I am
just starting my research.
 
I have restored two SB-200's so far during the past 10 years, but this is my
first pass at a '220.
 
What are the suggested and "aficionado-approved" or collector-recognized
modifications for this model, and where can I obtain the technical
documentation on these?
 
Thanks - Jack  W3RU 
 		 	   		  
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