Q I have a 10-year-old Realistic 13-inch color TV that I use with my ATV station. Recently the TV went completely dead. It won’t turn on when I press the ON button on the front panel, or when I try to turn it on from the remote. I checked the power supply fuse and it is okay. The power supply appears to be working as well. Any ideas?
A Many TVs operate in what you might call a “sleep” mode. That is, there are circuits within the TV that are active continuously—even when the rest of the TV is off. Usually the primary microprocessor is always active, waiting for the command to switch on the rest of the set. If the microprocessor isn’t responding to manual or remote “on” commands, the microprocessor could be defective. If you have a volt-ohm meter and a schematic diagram, measure the voltage at the Vcc pin of the microprocessor. Is it receiving power from the power supply (probably 5 V)? If so, find the microprocessor pin that produces the output signal to turn on the rest of the TV. Do you get a reading at this pin when you press the TV’s “ON” button? If not (and I suspect you won’t), the microprocessor is probably dead. On the other hand, if you do get a reading, it’s time to troubleshoot the rest of the circuit that is responsible for switching on the set. This is likely to include a couple of switching transistors and possibly an optoisolator.
From QST November 2000
