If you have a capacitor on the output of any linear
VR IC you must include a diode in series with the
input +V to protect the VR IC against reverse
current tht will result from removing power with any
DC continuity to ground. LM78xx and LM317 are
tuff ICs but I destroyed several before I learned
about the diode. A 1n4002~1n4008 will work fine
and they are dirt cheap. It iaslo a good idea to put
a 2 or 3 amp fuse in seriers for some overcurrent
protection.

Terry