E-O4 is an indication that there is a problem of data transfer between the video drum and its associated circuitry and can appear for something as simple a dirty video head, however if this does not apply then the head itself could be defective or the ribbon cable that connects it. Another reason can "occasionally" be that the mechanism has not returned to its correct stop position after having carried out an operation (load / unload etc) thereby not activating a position sensor, and its in these cases that some people find that lightly thumping (with hand) the bottom of the camcorder can correct the fault, or alternatively sometimes by pressing lightly on the cassette door. (although mentioned its generally later DF / DV models that this can apply to) Its a question of if this error comes on straight away after switching on? or does it only appear after a tape is inserted?