How can I fix my JVC DVD Recorder model DR-MH20S?

This unit is 5 yrs old and has served me well. Following repairs to damage caused by power cuts in November 2010, the machine works normally except that it will not return to standby when it is turned off after use after use, and within 5/10 mins of being turned off, it goes completely dead. The only means of restoring power then is to turn the power off and then on again at the mains, but the unit then needs to be reset, as if new, because the date and time settings have been lost.

Does anyone recognize this fault and know how to fix it?