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| Unexplainable design fault |
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| Pentoad:
Will try progressively isolating. I have also noticed that sometimes just touching the output of the voltage reference using my multimeter probe fixes the problem until the board is powered again. The multimeter wasn't even switched on when I did this. |
| jmelson:
--- Quote from: Pentoad on January 16, 2020, 07:59:40 pm ---Will try progressively isolating. I have also noticed that sometimes just touching the output of the voltage reference using my multimeter probe fixes the problem until the board is powered again. The multimeter wasn't even switched on when I did this. --- End quote --- Does the LM4041 need a capacitor across it? Check the data sheets for recommended operating circuits. It might be oscillating. Jon |
| Prehistoricman:
--- Quote from: jmelson on January 16, 2020, 11:24:47 pm --- --- Quote from: Pentoad on January 16, 2020, 07:59:40 pm ---Will try progressively isolating. I have also noticed that sometimes just touching the output of the voltage reference using my multimeter probe fixes the problem until the board is powered again. The multimeter wasn't even switched on when I did this. --- End quote --- Does the LM4041 need a capacitor across it? Check the data sheets for recommended operating circuits. It might be oscillating. Jon --- End quote --- I also thought this. Datasheet says none is required, but one may be used. |
| SiliconWizard:
--- Quote from: Pentoad on January 16, 2020, 07:59:40 pm ---Will try progressively isolating. I have also noticed that sometimes just touching the output of the voltage reference using my multimeter probe fixes the problem until the board is powered again. The multimeter wasn't even switched on when I did this. --- End quote --- Have you also just checked the soldering? |
| TerminalJack505:
That capacitor connected from U1A's output back to its non-inverting input has me concerned... That particular part can go into latch-up (or simply misbehave) if any of the I/Os go more negative than the GND pin. Also, the current into any of the I/Os must be limited to 10mA or less. Is that capacitor needed? You might try removing it to see if it helps. |
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