The tiny LED is a Nichia NSSW157T running at 80mA max. It's supposed to spew out 30lm with above 100lm/W and heats up close to untouchable without PCB contact. It's also equipped with an additional diode (0.7V drop) for reverse voltage protection of the LED chip.

The G4 replacement PCB uses a PT4115 buck controller, 68µH inductor, diode, electrolytic capacitor and a bridge rectifier. It is not as bright as the 20W halogen light bulb and much bluer, but my goal is to starve my utilities company and save every single mWh I can find ;-)