Since I never understood op-amps from reading or practicing problems I wanted to build a circuit to probe around and use different resistor values to set the amplification....
Is the ground for the voltage rail and input signal the same?
Yep.
What exactly is wrong with the circuit I built? I want the LED to only turn on when 5V is supplied at the input, right now the LED can turn on if I connect the ground to the voltage rail supply even without an input voltage.
Schematic of exactly what you did… not what was on paper, how it is on the breadboard.
I’ve seen the post on Adafruit with the feedback resistors connected to the same ground as the rail supply, but the circuit diagram does not show where the input voltage ground is? Link: blog.adafruit.com/…/ask-an-educator-making-a-non-…
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....
That doesn’t actually mean it’s OK, there are cases where transistors and other descrete components are “semi-burnt” (tests check out, yet it doesn’t work or doesn’t work as it should). The ”not so reliable" test would be to use a multimeter and see the voltage drop between B-E and B-C. The definitive test would be to make an actual amplifier circut, use the transistor in it and see if it works and if it distorts the sound (there are also cases where the PN substrates are somewhat depleted or damaged, either through use or a manufacturing error, so it works, but distorts the signal).
Do the light test, see if that passes, then do the multimeter test, see if that passes as well. If they both check out, 99% chance the transistor is OK. That 1% can be eliminated with the test circuit amp test.
Non-Inverting LM358 Circuit Not Working (discuss.tchncs.de)
Since I never understood op-amps from reading or practicing problems I wanted to build a circuit to probe around and use different resistor values to set the amplification....
Transistor particle detector not functioning as expected (voltage.vn)
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....