sb-100 problem

[W6CUX]

Hi Bruce,
Your problem is most likely an open 200 ohm balance pot -- these things 
are infamous for suddenly opening up. You should  replace it with a 
25-turn trim pot such as the Spectrol 64W201 or Bourns 3296W-201. These 
are .375 x .375 with three wire leads out the bottom and the screwdriver 
adjust out the top. Both are available from Mouser for around $2.00. 
They would  mount in the same holes as the original pot but on topside 
of the board.

The diodes should be Schottky types such as 1N5711 (DO-35)  which are 
also from Mouser at 0.13 each. Logic diodes such as the 1N4148 won't do.

73, Stu W6CUX

Bruce Wiedmaier wrote:

>Hi all
>
>I have an sb-100 with very low output in ssb but tune is full output. I replaced all resistors on the modulator board after i found 4 of them way off that made things worse. I have swaped tubes out of a working  sb 102 and there was no change. I changed the balanced modulator diodes
>also no change. Does anybody have any ideas about what is going on with this thing. Its been along time since one of these has stumped me like this.  
>
>
>         Bruce  WD0JGet more from the Web.  FREE MSN Explorer download : http://explorer.msn.com
>
>  
>

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