Melos is (in)famous for not providing a single bit of schematic information for any of their products.
Which, in the end, is a bit of a psychotic position.
This is high end audio, and the circuits aren't exactly a continental level state secret worth withholding for 30 plus years.
This is the kind of thing we tend to find out at at the end of the deals, not prior. As in 4-5-7-10-15 years down the road from when we first purchase the unit new. When failures start to appear, when the units are out of warranty... or the given company is gone.
Nevertheless, there are extant technicians with experience in the Melos gear.
But ...self repaired by someone who has not had their hands inside these sort of units before, and/or is used to working with no schematic? Those people are thin on the ground.