D1 has nonsense. Replace it with a short circuit. On Sat, Jun 27, 2015 at 4:27 PM, Bob Blick wrote: > RB4 is floating, that's the problem. > > On Sat, Jun 27, 2015, at 05:35 AM, P Nielsen wrote: > > > > PIC 16F628A-20 Sine Generator - Erratic Behavior on Vero > > > > Please see the circuit diagram here at box.com: > > https://app.box.com/s/my4upsstcu1tjlhkvi00cu4fvaprp01e > > > > The PIC is programmed to produce 5 selectable frequencies using wave > > tables. The PWM output is filtered into a sine wave via a passive LP > > network. It is powered from a good variable lab supply. > > > > The voltage reference disables a flashing LED when the battery is low. > > > > The problem is that after successfully building the prototype on a smal= l > > piece of Veroboard, I cannot get it to work anywhere else. In particula= r > > on a larger Veroboard or a solderless proto board. I have tried > > everything I can think off ... several times. The PWM output looks fine= , > > but as soon as I connect the filter cap to deck, the signal dies. This > > does not happen on the original build which is exactly the same circuit= .. > > > > I have installed a 104 cap across the rails and shortened any unused > > tracks to no avail. > > > > What is the recommended troubleshooting procedure for a situation like > > this. > > > > Can anyone offer any suggestions? > > > > Paul Nielsen > > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.fastmail.com - Faster than the air-speed velocity of an > unladen european swallow > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .