hifi engine

Sanyo boombox M9998 L


Got this boombox,put a new motor in it, replaced reels as they were cooked, now works amazingly nice.However, auto stop keeps kicking in driving me maaad, even it I run it with no tape. Any clues?
Cannot find in service manual anything about how auto stop works.. it should be possible to perhaps make it less sensitive or what exactly could it trigger it? How does the autostop work on these monsters?

Thanx a bunch !