I'm in the US, but have a Nakamichi BX-300E that's sat, unused, with family in the UK for 20 yrs or so... They don't have a system to hook it up to, so I'm wondering if there's anything I can ask them to check? (other than plug it in; make sure it doesn't go bang ;) It'd be nice to have a sense of whether it works, or not, before offering for sale, even "as is". Grateful for guidance on possible simple, remote, tape-less testing. Thanks.

The most common failure mode on these old Naks is the rubber belts and the idler tire in the transport mechanism. I just rebuilt my parents' CR-3A, which I believe uses the same Sankyo transport as the BX series, and the belts had turned to soup. Replacing the belts, idler, and electrolytic capacitors in the power supply (more a precautionary measure than an actual repair) brought it back to life.

To test the transport function they'll either need a tape or locate the little lever that depresses in the presence of a tape. Manually operating that lever will make the machine "think" there's a tape in the transport and will enable the transport controls. It should also spin the take-up reel a few revolutions to take up any slack in the cassette. If it doesn't, the idler tire is probably toast. Press "Play". If it immediately reverts to "Stop" the capstan drive belts are no longer. I would expect all the rubber bits to be completely perished.

Thanks for the thorough reply - much appreciated. Was it easy to source the belts & bits for your parents' CR-3A?

No. It took some poking around the dusty corners of the interwebs, but I did find eventually find a supplier of what appears to be OEM quality belts. I'll forward you the link if I can dig it up again.

In addition to the excellent post from markiteight I should mention that the worst thing for the Nakamichi transports is sitting unused. The rubber parts almost always fail if not used regularly, although they can certainly fail even if used. His recommendation of replacing rubber belts and idlers and electrolytics is a very good idea. It can also be tested by just sticking in a cassette - an unimportant one in case the transport damages it - and seeing if it plays, rewinds and fast forwards. Although it is quite possible to work for a tape or two and then fail if the rubber is questionable, so I'd recommend the replacement of those parts.

Thanks indeed to Mi8, and to you Tom for confirming the 'diagnosis'.