There are a number of sites on the internet that support electronic keyboards/synthesizers for OEM and aftermarket parts, manuals and repairs. Most however do not have a large inventory of semiconductors, diodes, transistors or that impossible part that is no longer available from your keyboard manufacturer. A replacement EPROM for a DX7IIFD is a perfect example, which I scoured the planet for, until finding this great source in the UK. Check out the link below, click on "service manuals", pick your manufacturer, and a huge inventory of parts/chips become available.
Link: http://www.wdgreenhill.com/index.htm
