My power supply cord quit working. I ordered a new one with the same numbers as my old one 24VDC 500ma is called an AC adaptor.Mine had a single line with a red and black wire inside. The new one had a double black wire with dashed lines on one. So with the new one I get a long blink.I have 2.5 pin.What is it that I have to look for to get the correct cord. Todd700