Hi mate,

Seems the previous thread got lost in the ether,

but pin6 and pin 7 on U16 are inputs from the address bus from either U8, U9,U10, these are fed from connector J3, didnt we have a zero signal from here somewhere?

I was getting some strange readings from U7 to U11, so I replaced / socketed the lot.  I have a bit of an anomoly with Clay's guide for testing the 4049's.  Red to pin 8, black on 2-7, 9-12, 14-15.  On mine, U7, U9, U10, U11, U12 and two new ones are all getting null readings on pin 9.  However, on U8, I'm getting a reading?????

**Scratch that re U8.  Pulled out the chip and getting same reading.  Replaced it with another and now they are all the same....But still pin 6 on U16 null....Could this be a bad UDN?