The circuit I'm attempting to construct:
I'm constructing the circuit shown in the above image, but I'm experiencing strange behavior when I solder on the switches and test the circuit. The switches are normally closed and are meant to break the connections between the NOR gate inputs and ground. The NOR gates (NTE74S02 TTL gates) are arranged as a SR NOR latch that is meant to turn on the lamp when the switch attached to the SET NOR gate's input is opened and turn off the lamp when the switch attached to the RESET NOR gate's input is opened. The voltage source is 5V DC.
After soldering on the switches and connecting the voltage source, the lamp is meant to remain off until the SET switch is pressed. It is meant to turn off when the RESET switch is pressed. However, the lamp remains persistently on when the voltage source is connected, even after I press the RESET switch a few times. Here are pictures of the solder joints connecting the SET switch to the SET NOR gate:
The circuit works as intended if pressure is applied to the completed solder joints on the contacts of the SET switch. This behavior suggests that the joints are cold joints, but use of a multimeter indicates that the joints are in fact connecting the switch contacts and the wires. I also made sure that I used flux on the contacts and the wires.
Has anyone else encountered a similar problem with solder joints?