This part is a kind of semiconductor called S3D.

Function of this product has General-Purpose Rectifiers.

Manufacturers : Fairchild Semiconductor

Image and pinout :

Some of the text within the PDF file :

S3A - S3N General-Purpose Rectifiers May 2015 S3A - S3N General-Purpose Rectifiers Features • Low-Profile Package • Glass-Passivated Junction • UL Flammability Classification: 94V-0 • UL Certified, UL #E258596 SMC/DO-214AB COLOR BAND DENOTES CATHODE Ordering Informations Part Number S3A S3B S3D S3G S3J S3K S3M S3N Top Mark S3A S3B S3D S3G S3J S3K S3M S3N ELECTRICAL SYMBOL Package DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) DO-214AB (SMC) Packing Method Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Tape and Reel Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the [ ... ]

S3D PDF Datasheet Download