Have 2 Of These Dvd/vcr Recorder/players, Both Have The Same Problem.

Machine #1:after one of the uses of vcr,tape ejected,both tape & dvd lights came on and power shut off.On trying to turn back on,both vcr & dvd lights come on and apx.1 second later power shuts off.Machine #2: After using a tape,pressed rewind,tape rewound,did not eject,both dvd & vcr lights came on and power shut off.To get tape out,removed outer shell,rotated motor shaft and belt until tape ejected.At this point,machine operated properly in dvd mode until a tape was used again,then same problem.Rotating motor shaft no longer corrects problem.I have over 30 years in service of electronic organs,not vcr's,and as a guess i feel there is probably a micro-switch or sensor that tells the CPU whether a tape or disc is being used.However I cannot find it or how to get vcr section out to check underneath.I would be satisfied if I could disconnect vcr and only use dvd section.