[Heath] More SB-200 joys...

[G3OOU at aol.com]

Hi Ken
 
Thanks for the update on the SB200 work.
 
I am in the final throes of refurbishing an SB-101 to which I had  
previously added top band. 
 
Had to change about 30% of the half watt carbon resistors which had all  
aged high and well out of spec. 
 
The LMO switch needed a good clean and I found a leaky 6AU6 at V3 which had 
 a major effect on Rx AGC. Substituted an IEC type which works fine.
 
Changed the Rx RF stage to a 6HS6 which increased the sensitivity somewhat  
but not surprised as the slope is almost twice that of the 6AU6 - will not  
help with the dynamic range though as 40m is very busy in the evenings with 
 large BC signals. The heaters also needed re-balancing as the 6HS6 takes  
450mA which is 150mA more than the 6AU6.
 
The S meter zero preset pot also needed changing and the PA neutralising  
adjusting.
 
Works much better and gives 100W plus on all bands except 10m where it  is 
about 90W. Now I just have to find a replacement bandwidth knob, box it  up 
and move on to the next project.
 
73

Bob

Bob F Burns
C Eng,  FIET, MSE
Amateur Radio Callsign: G3OOU
Registered RSGB  Instructor
G-QRP Member No: 6907; Zone: 14, QRA: IO91WH; WAB:  TQ25
Secretary of Crystal Palace Radio & Electronics Club: _www.g3oou.co.uk_ 
(http://www.g3oou.co.uk/) 
Technical web site: _www.qsl.net/g3oou_ (http://www.qsl.net/g3oou) 
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