7805 Regulator Outputs Voltage Too Low

[Pyrze4132]

So, I built a power regulator from a 7805 and a few capacitors. I hooked it up to a 7.4v li-ion battery and tested it with my multimeter. It output exactly 4.95v. I then hooked it up to my fc yobo, but the yobo didn't turn on. When I check my regulator again, while hooked up to the system, it now only outputs around 2.2v.

Is this normal or did I screw something up along the way? Either way, how do I fix this so when the NES is on, the regulator outputs the correct voltage? I can provide pictures, if necessary.

 

[bentomo]

What is the size of the 7805?

Voltage sources can drop under load depending on the current requirement of the device itself.

And as per usual check for any shorts or bad wiring with a meter.