[Raleigh]

I had a similar problem with a much simpler radio after I took the chassis out to measure the AVC voltage. When I put it back together I discovered a tube had mysteriously blown a filament (probably my ham hands with the meter). When I replaced the tube, the radio would only receive the lower half of the dial.

I tore my hair out trying to think of anything that would cause such a sudden loss of the upper frequencies. As a last resort, I walked through the alignment from start to finish, and darned if that wasn't what it was. I still have no idea what caused it, but careful alignment fixed it.

Your radio is much more complex, of course, so that might not be it.