Okay lol that’s funny. I was watching those videos waiting for the guidance on the top cover, but also thinking “Daniel is going to figure this out before I come to a conclusion…” haha. I was right.
Glad you figured it out. When I saw in the video there was a screw hiding up there by the PSU assembly I thought “that’s the one.”
The manual actually does show the screw, the problem is the exploded view doesn’t clearly represent the screw fastens to the top cover. Typically, in this case, there would be a dashed line from the screw through the metal chassis to the receiver on the top cover, but there is no line. See pic below…I highlighted in pink color the specific screw and the receiver…no dashed line. This leaves the reader, unless familiar with the 246 assembly, to assume the screw fastens to the metal chassis. The reader would have to make some critical observation and deduce, according to the drawing, the screw then (if fastened to the steel chassis), fastens nothing, and then conclude something is not right and there must be something else to which the screw fastens. But it is hard to know, and for somebody not familiar with the 246 assembly it would be a guess at best. It’s so interesting to me the major shift in the quality of the manuals for Tascam devices during this era. If you look at the manual set for the 1st generation 122 series and 244 compared to, for instance, the 122mkII and 246, the Service Manuals reduce in page count by about 50% or more as do the Operations Manuals…no theory of operation, no background explanatory educational stuff, actual service procedure instructions are more brief and less clear, etc. And the later manuals have a much higher frequency of errors, so I’m not surprised the 246 Service Manual leaves something to be desired here. Off the top of my head the Service Manual for the 1st generation 122 is (ironically) 122 pages, and the 122mkII Service Manual is less than 60 pages.
The guy in the videos, yeah he moves pretty quick, but it’s also a good representation at the other end of the spectrum of what kind of handling these devices will tolerate. What you can’t see is all the small movements or certain pressure he puts on the connectors, for instance, to make the disconnection easier, so it looks like he’s just tearing them off, but if one slightly flexes the connector plug away from the latching tab and rocks it a little it slides off pretty easily. Yes, care should be taken, but you do it enough and that’s what it looks like when unplugging stuff after developing some technique with experience.
. It looks like it sat a long time, dusty with some cobwebs. The pinch roller and idler tires cracked, haven't touched them yet, hopefully they won't turn to goo when I clean em up like the belts, which were totally melted and all over the bottom (like your 244 Cory) - makes me think they were the original never changed.