Apple iMac A1418 logic board boardview for board 820-3302-A, marked D7 MLB DVT, supplied as a 174 KB ZIP. Apple numbers its logic boards 820-xxxx with a revision letter, and DVT denotes a design validation test build, so minor differences from production boards are possible. Open it in a viewer like OpenBoardView or FlexBV to locate components, nets and test points when diagnosing power or display faults. Check the 820 number and revision silkscreened on the board before trusting the layout.
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 @cynetitsolution. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.