1N750A is the part behind this 50.3 KB PDF, a datasheet for a member of the JEDEC 1N746A to 1N759A zener diode family, catalogued here under schematics. Expect a table of zener voltages and impedances, maximum ratings and a drawing of the axial glass package. Repair technicians consult it to confirm the breakdown voltage when a supply or reference line reads wrong, and to pick an equivalent part. The cathode stripe gives orientation, and the A suffix tolerance should match the original when replacing.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.