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Does it work to 100% with alkaline batteries? Your NC-3 pack may have seen a lot of charges in its life. Try the AA alkalines before you back-burner it. The Red/Green blink should come on with fresh alkalines.
The red/green LEDs should blink with NiCd or NiMH cells unless they are nearly depleted. I can't remember exactly, but the input only needs less than 4.5V to reach the 330V output. That was done to allow for a fast full recycle time since there is the (crude) pulse regulation to prevent overvoltage on the output.