I have more space so i could use a 555 timer.
So. The 555 timer will a high signal at 1hz rate.
Then there are two red leds. They blink every second. i used them because i didnt use 7-Segment display on my full.clock. if you dont want them to blink just connect to the 4v unused output and replace 50 ohm resistor for a 35 or 40 ohm
Logical Operators
UNIT SECS:
1-AND Gate to pins B D. This gate gives true while both pins has a High signal. It ll give a High signal to reset on the unit secs counter. (Will reset when counter value reaches hex A).
TEN SECS
1-AND Gate to pins B connected to ten secs counter and up on next counter. (Will reset when reaches 6).
MINUTES
I included the unit min counter without decoder and display. Minutes construction is the same as seconds. Since it has the same conditions.
Clock 24hs Full Assemble
http://everycircuit.com/circuit/5422850782527488
Clock Tutorial N 2 Hours Counting
http://everycircuit.com/circuit/6171646638424064