Content originally posted in LPCWare by elef on Sun Jul 15 06:13:10 MST 2012
Which "positive" did you connect scope GND to?
If it was the 5V then most likely the input diodes (or your USB port on the PC).
If it was the 3.3V, 1.8V or 1.2V, then most likely the onchip regulator(s) on the LPC3154. Are you getting 3.3V, 1.8V or 1.2V anywhere on the board or out of the LPC3154 at the TP's (test points)?
Either way, i would start with input diodes, check you are actually getting 5V to the LPC3154 power input.