Be sure to add me to your favorites list Yamaha Original Service Manual for the PSR-28 Portatone Electronic Keyboard. Great, original Yamaha service manual for the PSR28 Portatone keyboard synthesizer, cousin model to the PSR-27. This has the specs, panel layout, the full parts list, exploded views, and includes the large overall circuit diagram as well. It's in very good ++++ condition, looks unused, like new old stock that was in storage. This is a manual or document, this is NOT a piece of equipment or instrument. If you have any questions, I'm always happy to answer them. Thanks for looking! Check out my Store!