When did James Watt conceive of the separate condenser?

James Watt conceived of the separate condenser in May 1765.12

While repairing a model Newcomen steam engine in 1764, Watt observed that the engine's single-cylinder design resulted in a significant waste of steam. After studying the problem, he realized that the loss of latent heat was the engine's primary defect and concluded that condensation needed to occur in a chamber separate from the cylinder. This invention, which he later patented in 1769, became the foundation for the Watt steam engine, a critical advancement during the Industrial Revolution.321