I called about the MK160 problem to velleman support they sent me a LM 741 IC it still has the same problem the led comes on but does’nt trip the relay.Can it be fixed with the LM 741 or does it need the TL071 or the TL271.THANKS
No, it should work than.
Check pin 2 of IC1, R9, T1 and their connections to each other (on continuity and short circuit). Measure if the PIC (IC1) is powered: 5 Volts between pin 1 and pin 8. If all this is ok AND the dip switches are set correctly, IC1 will be defective.