NT-1431 information
It's been a long time since I last saw one of these monitors, but one just came in for repair. I'm photographing it now and preparing lots more information to go into my repair guide for this model.
The NT-1431 was one of the monitors (VGA resolution) to be installed into the Medalist "Spectrum" (a.k.a. Spectrum Genesis) coin op dart machines. I have not been able to locate a manual or schematics for this particular model, but you can use either the Neotec NT-27V or the NT-2702 (Li-Chin version) manuals and schematics to troubleshoot this monitor. Notice the neckboard says, "Li-Chin" on it.
This model is installed in a special custom made frame specifically to fit the odd shape of the Medalist Spectrum dart machine cabinets. The remote adjustment board is long and skinny with trimpots R503, R502, and R501 NOT installed.