I just took a look at the service manual - excellant, very detailed, especially the diagrams re. the automatic mechanism - have you cleaned and re-greased the relevant parts?
I doubt that is the source of your problem but a maintenance regime is a must with all audio eqipment.
Take a look at the PSU/PCB - you may see a cap or transistor has blown (my 990 has a clearly burnt out transistor). If there is no obvious problem then do a continuity check on all components, then get back to the forum.