The 74xx series TTL is not necessarily compatible with 4000 series CMOS logic ICs.

The 4000 series has a much wider range of voltage for operation; ~3v to ~16v; some go up to 18v. The 74xx series is generally restricted to a range of 4.5v to 5.5v to ensure proper operation. Some 74Hx ICs have a somewhat wider operating voltage range, but nowhere near the 4000 series.

 

AND gate IC another name 7408

7408 is TTl ( transistor transistor logic)
4081 is CMOS ( complemented metal oxide s/c)..

Use CMOS chip.........

 

I use diode gates quite a bit. My personal rule for using them is they must feed into a powered gate. You can alternate indefinitely that way, diode gate, powered gate, diode gate, powered gate, etc. They are good for that large gate configurations you occasionally need, like 10 inputs or whatever.

I also have a good website to use as a reference to find logic (like those pesky AND gates).

http://users.otenet.gr/~athsam/database.htm

 

Awesome, thanks, I completely forgot that diodes do the same thing
I shall be doing that then to save on chip count if the 4017 can sink current (I'll check the sheet)
I think that between the alarm and the blinking colon I added another 2 pages to this schematic

 

You might find this Wiki entry interesting from a historical perspective:
http://en.wikipedia.org/wiki/Resistor–transistor_logic
Follow the links in the entry to learn more about other technologies.