Bad Power Supply Voltages

Hello,
I have a DIY v2.1U board that has been working flawlessly for several years, until last summer that is. Then it became difficult to connect to without restarting, but it still ran the scheduled programs. I have finally gotten around to troubleshooting it and after a bit of looking, discovered that the 3.3V output intermittently would go to about 1.6V which caused it to stop working. I started removing the IC’s that I could (display, Enc28J60 (IP interface), CPU, then and finally, the SD card) checking the 3.3V line after each removal. on removing the SD card the voltage went back up, but now to over 4VDC! Replacing any item brought it back to ~1.6V. I removed the 3.3V surfact mount regulator intending to replace it, but discovered that I did not have any here. Part is not specifically identified on the schematic so I am wondering what is the anticipated current required for this output? Does anyone know?

Note, I plan on using a leaded part and “dead bugging” it on the board – much easier than trying to reinstall a surface mount part in the limited space.

Thanks in advance.
Vince