In electronic systems a diagnostic board is a specialized device with diagnostic circuitry on a printed circuit board that connects to a computer or other electronic equipment replacing an existing module, or plugging into an expansion card slot.
A multi-board electronic system such as a computer comprises multiple printed circuit boards or cards connected via connectors.
Simple standard diagnostic plug-in boards for computers are available that display numeric codes to assist in identifying issues detected during the power-on self-test executed automatically during system startup.
The concept can become unworkable when signal timing is affected by the length of the signal paths on the diagnostic board, as well as introducing Radio Frequency Interference (RFI) into the circuit under test because of a lack of adequate shielding.
Vector Electronics & Technology in North Hollywood Calif. is one of the few companies still making these legacy boards.