There's an old Irish tale, of a man who stopped and asked for directions to a small town, and the reply was, "If I were you, I wouldn't start from here."
I similarly believe, that if you want to start out fixing test equipment, a precision 6.5 digit meter isn't the place to start.
Having said that, can you do a full set of tests, with various AC and DC voltages, currents and resistor measurements and let us know what it says. I'm not sure if the service manual is available for this, and if it is whether it has schematics, but check the power supply rails, both with a meter and with a scope to make sure they are ok and not noisy. If that all checks out, undo and reseat every connector in the instrument, check electrolytics for swelling and let us know how you get on.