Low voltage in J-Box

Hey guys;
Just powering up my unit and was checking voltages. I have the 5 v
regulated power supply and all is well until I plug in the QC100's. I
get a voltage drop when each is plugged in and the supply is down to
about 1.5 volts when all three are in the jbox. I programmed the IC's
and the program was successful. Also, as expected,the regulator U1 is
getting hot. Any ideas up front before I start disassembling?? Thanks
in advance. BTW, all conncectors to the scales and dro have not been
connected yet. This is just the bare board with the 100's attached.
Some start huh??? Thanks in advance.
Me