Tektronix 2445, Instruction Manual

Page: 101 / 351

Performance Check— 2445 Service
8. Set CH 1 and CH 2 DC Balance.
N O TE
For an accurate D C Balance setting, the instrum ent
M U S T be allowed to warmup for 2 0 minutes before
perform ing the following steps.
VOLTS/DIV
CH 1 and CH 2 2 mV
Input Coupling
CH 1 50 G DC
CH 2 1 Mfl DC
A and B SEC/DIV 1 ms
a. Press up and hold both the CH 1 and CH 2 Input
Coupling switches in the 1 Mfl AC position for approximate­
ly 1 second, then release them.
TRIGGER MODE
SOURCE
COUPLING
AUTO LVL
VERT
NOISE REJ
N O TE
A t the completion o f the autom atic D C Balance, the
Input Coupling settings will return to the states they
previously held (if they were in those states fo r a t least
7 seconds prior to performing the D C Balance
procedure).
b. Connect a 1 kHz, 2 mV standard-amplitude signal
from the Calibration Generator to the CH 2 input connector
via a 50 fi BNC cable.
c. Connect the CH 2 signal from the rear-panel CH 2
SIGNAL OUT connector to the CH 1 OR X input connector
via a precision 50 Q BNC cable.
b. VERIFY— A moving dot display replaces the normal
display for approximately 10 seconds (while the DC Balance
levels are automatically reset), then the display returns to
normal.
c. VERIFY— There is less than 0.2 division vertical trace
shift between adjacent settings of the CH 1 and CH 2
VOLTS/DIV switches as they are rotated through each of
their positions.
d. VERIFY—There is less than 1.0 division vertical trace
shift as the CH 1 and CH 2 VOLTS/DIV VAR controls are
rotated fully CCW.
e. VERIFY—There is less than 0.5 division vertical trace
shift when the INVERT button is pressed in.
f. Return the VERTICAL VAR controls to their detent
positions and turn the CH 2 INVERT function off (button
out).
9. Check CH 2 SIGNAL OUT and Cascaded
Operation.
a. Set:
VERTICAL MODE
CH 1 On (button in)
CH 2, CH 3, and CH 4 Off (buttons out)
BW LIMIT On (button in)
d. CHECK— Display amplitude is 4.5 to 5.5 divisions
(discount trace width).
e. Set CH 1 Input Coupling to GND and align the trace
with the center graticule line.
f. Return CH 1 Input Coupling to 50 S2 DC.
g. Set the CH 1 VOLTS/DIV switch to 5 mV.
h. CHECK— The baseline of the display is within 2 divi­
sions of the ground reference set above (discount trace
width).
i. Set the CH 1 Input Coupling to 1 Mfi DC.
j. CHECK— Display amplitude is 3.6 to 4.4 divisions (dis­
count trace width).
k. Disconnect the signal from the CH 2 input connector.
I. Set the CH 1 and CH 2 Input Coupling to 50
Q
DC.
m. Press and release the BW LIMIT button to turn the
function off.
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