Datasheet for the SN7438N, a quad 2-input NAND buffer with open-collector outputs, in a plastic DIP package, provided as a 22.8 KB PDF. It gives the pinout, function table, output sink current ratings and timing. Open-collector outputs need an external pull-up resistor, so a missing or open pull-up is a common reason for a stuck-low or floating line. Use the sheet to check output levels, and confirm the exact marking before you substitute.
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 @datasheet_technar_org. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)