Mr RB
Well-Known Member
Yeah I saw that was discussed and I agree with you completely it should have 120 ohms for that ciritcal resistor not 330 ohms.
BUT that is the not the primary symptom he is getting. It is dropping to 1v etc when any loads are applied. Now when the output drops to 1v there will be <1.2v from LM317 Vout to Adj, so the LM317 MUST turn hard on and supply a lot of current to the load. That is regardless of the resistor value.
The most likely scenario is a wiring problem. For example if he has the load connected to the Adj pin instead of Vout, it will act like a constant current regulator and supply only 1.2v@330 ohms or 3.6mA, that might explain the symptom.
Or if the LM317 pins are reversed etc that might also explain the symptom where it can't provide any significant current to the load.
BUT that is the not the primary symptom he is getting. It is dropping to 1v etc when any loads are applied. Now when the output drops to 1v there will be <1.2v from LM317 Vout to Adj, so the LM317 MUST turn hard on and supply a lot of current to the load. That is regardless of the resistor value.
The most likely scenario is a wiring problem. For example if he has the load connected to the Adj pin instead of Vout, it will act like a constant current regulator and supply only 1.2v@330 ohms or 3.6mA, that might explain the symptom.
Or if the LM317 pins are reversed etc that might also explain the symptom where it can't provide any significant current to the load.