In Reply to: Re: PCB problems please help posted by Darren on 11/28/01 at 5:26 AM:
Here are some guesses which might help:
Are there any high impedance nodes in the circuit which could be slowly charging/discharging due to leakage currents?
Also, where do the input bias currents from the LM324 '+' and '-' inputs go? Maybe one of these has no D.C. path.
I doubt that there is a heat problem within the circuit itself (given 10mA @ 5V) - but are there other heat sources outside the circuit? Voltage offset drift within the LM324 (or a differential amplifier made from transistors) could be a problem, especially if there is high D.C. gain in the circuit.