Hello,
(Please see attached schematic)
I have a set of 6 simple LED's that are each hooked to the single pole side of their own SPDT switch. The other poles are connected to a 5v source and 0-5v square wave signal source fed from a ZTX458 transistor. The switch selects between these two sources with the LED's activating when the square wave signal goes low (they blink).
My problem is that when the switch selects the square wave source, the fourth LED (from the left) fails to blink. The rest of them do. I checked the LED and it was not defective. When I measure the voltage drop on this LED I get 1.7v as compared the 0.4v I am getting with the other LED's.
When I remove this fourth LED, then the fifth one fails the blink. I used a 330 ohm resistor for this one because I ran out of 380 ohm resistors. I am wondering if this is the problem because the currents are not evenly distributed to the LED's? Any insight is greatly appreciated.