For the uninitiated, the (often mistaken for a standard HF transceiver or early digital scanner, depending on the market variant) is a classic piece of late-70s/early-80s Japanese engineering. It’s rugged, surprisingly sensitive, and an absolute nightmare to troubleshoot without the original documentation.
And that’s the problem.
A retired technician in the Netherlands (call sign PA0KLT) had scanned his copy. It is hosted on a private radio restoration forum, but I have uploaded a mirrored copy to my Google Drive for the community. Digi Di-166 Service Manual