TheOne
New Member
:idea: Make sure you don't have a PNP in place of Q1 with the emitter tied to the 9v (10v). This would also cause the buzzer to stay on. Check and double check your circuit. Also check that Q1, if not a PNP by mistake is not faulty. I often use a simple trick (after voltage measurements to identify the culprit and before desoldering ) to check transistor switching in low power circuits by briefly shorting the b-e junction of a transistor to force it to turn off, when on.
Make sure that you have not created a "mirror image" of the circuit on the pcb. I have seen this a lot with 1st pcb attempts by students! If this is the case the components needs to be soldered to the track side of the pcb to correct the error. (which gets real messy when IC's are involved, as the legs have to be folded back in the opposite direction so the device is actually upside down)
Make sure that you have not created a "mirror image" of the circuit on the pcb. I have seen this a lot with 1st pcb attempts by students! If this is the case the components needs to be soldered to the track side of the pcb to correct the error. (which gets real messy when IC's are involved, as the legs have to be folded back in the opposite direction so the device is actually upside down)