The PIC in the diagram below is programmed to produce 5 frequencies grouped around 40Hz. It outputs a 5Vpp PWM signal.
This passes fine through R9 and R10, but as soon as I connect either of the 473 caps to ground it kills the signal.
I don't understand why. It's just a passive filter and the PIC seems to be working normally.
I have tried everything I can think of. Can anyone suggest a solution?
David King