[Hallicrafters] SX-71 Restoration

[Julian Bunn]

Hi Gary,

Your mod is very similar (if not identical) to a mod described here:

http://pcbunn.cacr.caltech.edu/jjb/Hallicrafters/SX71/SoupUpYourSX-71.doc

which came to me from Rodney Bunt (although I don't know if Rodney is
the author of the document).

Oddly, on the SX-71 Run4 I have, and a Run 3 I sold on Ebay, that 2nd IF
cathode resistor is already the same value as in the 1st and 3rd. IF.
Which suggests that this mod was either made at the factory, or by owners.

Julian

GBrown wrote:
> For those of you that have a SX-71 or those that are going to restore one.
> Here is a little tidbit of info that mite make your day. I have just
> finished restoring a SX-71, from knobs to ant terminal and very satisfied
> with the performance on the lower HF bands. I thought that the upper HF
> bands were needing a little more gain. A look at the original schematic
> shows the cathode resistor on the 2nd IF as being 1000 ohms. CHANGE IT to
> 270 ohms like the 1st and 3rd IF are. I honestly think your going to like
> the added gain on the upper bands.
> Regards,
> Gary...WZ1M
> 
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