I recently bought some Texas Instruments TTL chips. So far they've been OK, except the XNOR (SN74HC266N) chips (I've tried 3, including one that's never been in my "real" circuit) always output low no matter what the state of the inputs are.
They weren't working right in the real circuit, so I pulled them out to test them in isolation. Maybe I'm not testing them right, but here's how I did it:
---- Input1 - - Vcc Input2 - - MM Probe (+) - - - - - - - - Ground - - ----
Where Input1 and Input2 where tied either to ground or Vcc of my supply (5.25v as measured by the meter). I expect the "Y1" pin above to measure near Vcc with respect to ground if Input1 and Input2 are either both high or both low, but the meter measures ground no matter what.
Am I testing this thing wrong, or do I have a bad run of chips? Am really new at digital electronics, so I'm fairly certain I've done something wrong.