Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Sounds like the second IC isn't getting the right reference voltage. You should have 1.25V at its pin 4 and 2.5V at its pin 7. Check those pin voltages, also the voltages at pins 4 and 7 of the first IC and the values of R1 and R31 (which connect to pins 7 of respective ICs).
Oh, that's a shame. Clutching at straws now; are you using leaded solder or lead-free (I'm thinking voltages measured on the circuit board may not be the voltages actually reaching the IC pins if there's a dry joint somewhere) ?
I'd assume that, too. I've not used lead-free and hope never to have to. By all accounts it can be problematic (difficult to tell a good joint from a bad joint, growth of tin whiskers etc)."Rosin-Core Solder" which I assume has lead in it.
Good. But that eliminates my last suspect . If any other possible cause of the problem crosses my mind I'll let you know. In the meantime all I can suggest is apply 5V (= 'full') to the circuit input, and double-check that every pin voltage (both ICs) is what it should be.I've been making a point to take all these recent measurements from the component side of the board (i.e. the actual IC pins) to avoid any such misleading measurements.