Quote:
Originally Posted by Geoff Harrison
No, unfortunately I don't have any current loop devices. I did verify that the 6850 was working correctly by connecting a TTL/RS232 adapter to its Tx/Rx pins, so if there's a problem it must be with the 7404 inverter (IC K, pins 8,9) or something on the incoming side (pin 9) of that. Do you have any way of testing whether a reasonable signal is getting to pin K9?
Geoff.
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Unfortunately, being a software person, I wouldn't even know what a reasonable signal is. Since the 7404s are socketed, would it help if I swapped them and see if the problem follows the current K chip?