[R-390] How to Make a R-725/URR

[Tom M.]

Gentlemen?

Someone asked me how to make a R-725/URR.

Ingredients:

-R-390A
-R-390 IF deck
-two IF-out adapters from the back of 390A junkers
-two short cables with BNC's on each end
-my article from Electric Radio, contact Barry at er@frontier.net

Simply follow the wiring modifications I described in the article (schematic is
included) and you will soon be enjoying the mellow sound of the R-390 IF deck
(or just get a R-390).  

The theme is to modifiy the filament wiring in the 390IF to work with the lower
voltages provided by the 390A PS.  You also have to drop the B+ on one or two
tubes to meet the gain intents for the R-390IF.  The adapters will allow
crossover for hooking up the signal cables.  

The result will be a 390 IF deck that you can drop into any R-390A anytime you
want that good sound (see also Chuck Rippel's simple audio mods).

Technically this is not a complete R-725 mod as it does not address PTO hum
bucking.

Questions welcome.

73 Tom N5OFF 

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