A ways back (on page 58) in this blog there's some discussion about modifications to a component - transistor Q3. Some models of the D18 have a heatsink attached, whereas some didn't. Mine has no heatsink. After 3 years of reliable use and good performance component Q3 smoked itself. After a brief smell of baking bakerlite and a whiff of smoke from the ventilation slots the sound became quieter, so I turned it off. After inspecting the PCB I noticed Q3 was cooked to the point it had turned to white, friable ash - to the extent I'm unable to read the part number. I'd guess its been on the way out for a while. Further, I think Yulong probably realised it was prone to overheating since they put a heatsink on (maybe) later models.
I contacted Yulong who haven't been particularly helpful, requesting the entire unit be sent back to them. Me, I'd rather take a punt and just change the component, but Yulong appear exceptionally reluctant to divulge what type of transistor it is.
I'm humbly requesting that any Head Hi-Fier who's got their D18 open and can see what breed the transistor is could tell me ? Thanking that kind person in advance.