Tektronix 2445A - Page 84

Performance Check-2445A/2455A Service
j. Move the probe to the Channel 2 input connector.
k. Set the VERTICAL MODE buttons to deselect Chan-
nel 1 and display Channel 2.
NOTE
Instruments with
TV OPTION 05 have a TV CLAMP
feature that
is enabled by pushing the upper CH 2
INPUT COUPLING button while
in AC COUPLING.
The letters TVC appear in the top right readout
when this mode is selected. Push the lower CH 2
INPUT COUPLING button to return to normal
AC
coupling.
I. Repeat parts c through i for Channel 2.
m. Disconnect the test setup.
3. Check CH 1 and CH 2 VOLTS/DIV, CH 2
INVERT,
þÿ”V and TRIGGER LEVEL Readout
Accuracies, Variable VOLTS/DIV, Vertical
Linearity, and
ADD.
a. Set:
NOTE
Select channels to set
VOL TS/DIV.
VOLTS/DIV
CH 1 and CH 2 2 mV
VERTICAL MODE
CH 1
CH 2
CH 1 and CH 2
BW LIMIT
HORIZONTAL
A SEC/DIV
þÿ”V
TRIGGER
MODE
COUPLING
4-6
On
Off
1 þÿM© DC
On
1 ms {knob in)
On {press and release for
a
ΔV V readout)
AUTO
DC
NOTE
The instrument must have had at least 20
minutes warmup prior to performing the following
steps.
b. Momentarily press and hold both the CH 1 and CH 2
upper Input Coupling buttons until a moving dot display
replaces the normal signal. This performs a
DC Balance of
CH 1 and CH 2 and the readout displays DC BALANCE IN
PROGRESS.
c. When the signal and readout displays automatically
return to normal, set the
CH 1 and CH 2 Input Coupling to
1 þÿM©
DC.
d. Connect the Calibration Generator to the CH 1 OR X
input connector via a 50 þÿ© BNC cable. Do not use a
termination.
e. CHECK-CH 1 and CH 2 VOL TS/DIV, þÿ”V,and
TRIGGER LEVEL readout accuracies
as follows:
1. Set VOL TS/DIV control to the first position listed
in Table 4-2.
2. Set the Calibration Generator STD AMPLITUDE
output
level to the corresponding Standard
Amplitude Input Level
in Table 4-2.
NOTE
To properly verify TRIGGER LEVEL
Readout Accuracy, the Calibration
Generator's STD AMPLITUDE output must
have rising and falling transition
times
(10% to 90%) > 20 ns. No overshoot
should appear on the waveform.
3. Verify that the generator output meets the
requirements noted above.
4. Use the VERTICAL POSITION control to set the
bottom of the signal
2 divisions below graticule
center.
5. Rotate þÿthe ” REF OR DLY POS control to align
the reference cursor with the bottom of the
waveform.