A typical problem reported on the Monitor III is "no video". In these cases,
adjusting either the contrast or brightness controls on the monitor solves the
problem. With an Apple II or II+, the problem lies in the computer's video
adjustment potentiometer, K14 on the main logic board. It is often adjusted
too low.
Before you send a Monitor III in for exchange, make sure that the monitor has
the problem and not:
1. the video cable or
2. too low of an adjustment of the video signal by the video adjustment
potentiometer, K14 on the main logic board.