hifi engine

Service manual Marantz receiver

I'm trying to find a service manual for my Marantz model 1520 ML receiver.
So far I've found manuals for model 1515/MR215/MR220 and model 1530/MR230/MR235 and these two are wrong even if I've found statements that 1520 and MR220 are the same receiver.

I have found Pictures of two significantly different model 1520's, and of what I can see there are a lot of differences inside as well.

Can someone here help me find a service manual for my 1520ML? It has an IC-output stage named STK463. I think that is the easiest way to tell the schematic diagrams apart.