[Heathkit] Differences - HD-1422 and -A model Antenna Noise Bridges

[Donald Spoon]

jack m wrote:
> Hi Gang,
>
>  
>
> I have an HD-1422-A Antenna Noise Bridge, but only have the HD-1422 Manual.  Anyone know what the difference is?  Circuit board in my "A" has same part number as shown in the non-A manual x-ray view.
>
>   
I have the 1422-A manual.  Comparing the schematic there to one I found 
on the web (http://tinyurl.com/yjgcj3t) for the earlier 1422, there are 
some wiring changes on Q101 and Q102.  R107 and R108 goes from the 
respective collectors to the respective bases on these transistors 
instead of from the +9V line to the bases.  There is an added .01 uF cap 
across the emitter resistor (R109) on Q102.  All the values are the 
same... only the additional cap and the wiring changes.  All the 
Heathkit part numbers are the same that are printed on the schematics.

Dunno what the impacts of these changes were....
>  
>
> Anyone know of a source for the 200 ohm pot?  Mine is burned.  Heath Part number is 10-1234 - a 200 ohm linear taper pot. 
>   
I can't help you here....  Sorry!

Cheers,
-Don Spoon-
K0APK