I recently built a couple of stripboard based boards using the DIP prop. Everything was working until at the last minute decided to add a couple of smoothing caps to the power. I added a 100 MicroF cap on to the incoming power (before the regulators) and a 47 MicroF Tantalum cap between pins 9 & 12. I didn't have space to put the tant on the other side and 47microF was what I had to hand at the time. I had wired in VSS and VDD to both sides of the chip.
After powering on, the program didn't run. I changed _CLKMODE to RCFAST and it works, but trying to use the external crystal results in hanging, even without specifying the '+ PLLnnX' part.
I have removed both caps and replaced the crystal on one of the boards but it still hangs, so I assume that I have damaged the chip. I don't have a spare prop replacement for testing the moment.
I have searched the forum and found that the PLL circuitry is sensitive to incorrect polarities and spikes, but as far as I can tell, the tant was wired the correct way around.
My question is - what caused the problem and what can I do to make sure I don't smoke the next chip ?
Background - I am a software developer and learning the hardware side, so please go easy on a newbie.