OK, here's the pins, what the logic probe says and what the voltmeter says: Pin Correct Name Rough Name State Voltage 8 2NOTQ Not Q Output High 3.93v 9 2Q Q Ouput Low 0.13v 10 2Set Preset High 4.99v 11 2Clk Clock Pulsing High 4.34v 12 2D Input High 5.02v 13 2Cr Clear High 5.00v D is driven directly from the bus so there's no chip driving it and the bus voltage looks fine. According to "Interfacing Microcomputers to the Real World" by Sargent and Shoemaker (the only thing I have that talks about the 7474 in detail, "The basic idea is this: with the clear and preset inputs high (not active), a transition of the clock input from low to high (called a positive edge) "clocks" the value of D into Q and the inverse into NOT Q. The clock transition is required; D can do anything it wants to, but nothing will happen to Q and NOT Q unless the clock has a positive edge." And the clock input is pulsing high so that's supposed to be positive edges. [THIS IS SO MUCH FUN!!!! SERIOUSLY!!! =-) ] And I don't see any fast pulse on any of the inputs that are supposed to stay stable. But what doesn't make sense to me is why the flip flop would fail in such a way that the outputs would be reversed with appropriate voltages. I feel I must be missing something but the poor thing is being driven in a pretty direct fashion...IE not alot of chips in the way and all the inputs look correct. I think I'm going to socket the thing and replace it with a 74LS74...if after two or three swaps (just for giggles) I get the same response, well then I guess I did miss something somewhere else. =-) In either case, I guess it's never a bad idea to socket things when you have an excuse in case something DOES go goofy. Anthony Clifton - Wirehead