[Boatanchors] Hallicrafters SX-99

[Richard Post]

Hi Dave,

Don't know if it's written up, but such a relatively simple mod would 
stabilize the oscillator.  A number of era receivers had regulated 
voltage to the oscillator stage.  For example, the RME-45 to RME-45B. 
The main change in that model was addition of a VR tube to the 
oscillator.  Helps especially in locations with power fluctuations.

Depending on how the mod was done, it may also have increased power 
consumption a bit.  Check power draw on the power transformer with 
the circuit in and out.(bypassed).

Cheers,

Rich KB8TAD

Boatanchor pix

http://tinyurl.com/hexco




At 9:26 AM +1200 7/30/07, Dave Brown wrote:
>Just acquired one of these, ex a barn for ? years,  in need of a new 
>power xfmr (well, apparently- not checked as yet).
>In cleaning it up I found there is an addition to the receiver in 
>the form of a small sub chassis (about 6 inches long-maybe 1.5 
>inches wide) mounted on top of the main chassis behind the 
>bandspread dial. It carries two VR105s and a large 5k wirewound 
>resistor.
>Does this sound like a modification that was written up anywhere? 
>Its been fairly well executed and looks at first glance like its 
>always been there. Not much too it, and hardly challenging to figure 
>out what it does, but be interesting to find out if it was described 
>anywhere in the literature.
>Dave, ZL3FJ
>_______________________________________________