Tektronix 3A9 Instruction Manual page 43

Performance Check/Calibration—Type 3A9
f. Set the VOLTS/DIV switch to 50 nV. down to the 50 .V position to obtain an on-screen trace at
50 pV.
g. CHECK—The trace should be on screen. i.
h. ADJUST—If the trace is not on screen, start at the
position of the VOLTS/DIV switch at which an on-screen dis-
play is obtained and readjust the Coarse DC Bal, working
ach control setting that has been changed from
previous setting will be shown in bold type.