Peter,
I have the 7000 Service Manual. I purchased it for an electronic service mans use as I know nothing about it. Alec mentioed some combinations some time ago but urged caution, if I remember correctly. The only key combination in the manual is for service: Hold C#3, D#3 and C#4 and turn on power. A series of screens allow tests of various sections of the 7000. Sure hope you can solve the problem.
Fran in SC