A quick visit to RadioShack's website all but verifies my theory:
-1779, the adapter I've been promoting for years, is listed as "Quantities limited, not available online."
-1775, the adapter you picked up, is listed as "NEW! Image coming soon" with a laundry list of special "features" including Energy Star compliance, etc.
Sounds like they are down to the last of the old (-1779) adapters, selling off simply what remains at the store level.
So I guess -1775 is the wave of the future as far as replacement TG-CD power supplies go.
That said, if the adapter is not working for you nod, your TG-CD interface unit is toast.