Cyclone III Development Board Failure

It turns out that these symptoms were caused by something malfunctioning on the 2.5V supply. After some trial and error, I determined that the malfunction was on the 2.5V circuit that powers banks 5&6 of the FPGA. The rest of the board functions correctly when R51 is removed.

To further troubleshoot the problem, I tried disconnecting everything besides the FPGA that was powered by 2.5V_B5_B6: bypass capacitors, analog mux (U35 pin 31). Unfortunately, removing the capacitors (and lifting U35 pin 31) did not solve the problem. So I am pretty sure that banks 5/6 of the FPGA must have suffered some internal damage that causes a short on this circuit. I'm posting this in case someone has an idea for something else to try.

Thanks very much,

E