Saul,
I have a 2901 also, found it at begining of this year in one of the many electronic junk stores in Sao Paulo. It was in a sorry state, completely covered in dirty. I don't know how it is yours, but a good starting point is to get a good contact cleaner and isopropyl alcoohol and clean all the switches. Also, all transistors are socketed, and they may have bad contact, so cleaning them is also a good idea.
Make sure you let it dry for a day before turning it on.
Terrahertz posted the link for the manual on this thread, so I won't be redundant. He and Bravov both made an amazing job with the teardown of their units, make sure you read this whole thread, it is unbeliavable how much one can learn from these guys.
Have fun with it! I understand it is an equipment with a very specific use (to calibrate scope time base) and may not be of much use outside of that , but it sure is a nice example of engineering.