Adjustment Procedure— 2445 Service
DAC REF, CH 1 AND CH 2 INPUT CAPACITANCE,
AND VERTICAL READOUT JITTER ADJUSTMENTS
Equipment Required (see Table 4-1)
Calibration Generator (Item 3)
Digital Multimeter (DMM) (Item 18)
50
Q
BNC Cable (Item 9)
Alignment Tool (Item 19)
50
2
Termination (Item 11)
Normalizer (Item 21)
See
ADJUSTM ENT LOC ATIO NS 3
and
ADJUSTM ENT LO C A TIO N S 4
a t the rear o f this manual for test point and adjustment locations.
Initial Control Settings.
Control settings not listed do not affect the procedure.
VERTICAL VOLTS/DIV
CH 1 and CH 2
0.1 V
CH 1 and CH 2 VAR
In detent
Input Coupling
CH 1 and CH 2
1 MQ DC
VERTICAL MODE
CH 1
On (buttons in)
CH 2, CH 3, and CH 4
Off (buttons out)
ADD, INVERT, and
BW LIMIT
Off (buttons out)
ALT/CHOP
ALT (button out)
VERTICAL POSITION
Midrange
A and B SEC/DIV
0.1 ms (knobs locked)
A and B SEC/DIV VAR
In detent
Horizontal POSITION
Midrange
TRIGGER
MODE
AUTO LVL
SOURCE
VERT
COUPLING
DC
SLOPE
+ (plus)
LEVEL
Midrange
HOLDOFF
In detent
At
On (At readout)
TRACKING/INDEP
INDEP (button out)
INTENSITY
Left of center
READOUT INTENSITY
As required for a visible
display
SCALE ILLUM
Fully CCW
FOCUS
Best focused display
1. Adjust DAC Ref (R2127)
N OTE
The objective o f this step is to make the total range of
the DAC output voltage (sum o f the C C W and C W
readings) equal to 2 .5 V.
a.
Connect the digital multimeter (DMM) negative lead to
the chassis ground. Connect the positive lead to pin 2 of
J118 (on the Main Board).
b. Set the DMM to measure approximately 1.5 Vdc.
c.
Rotate the AREF OR DLY POS control CCW until the
DMM reading remains at a constant value (approximately
— 1.250 V). Note the reading.
d.
Rotate the AREF OR DLY POS control CW until the
DMM reading remains at a constant value (approximately
+1.250 V). Note the reading.
e.
Add the absolute values of the readings noted in parts
c and d together (apprcxima tely 2.500 V).
f.
Subtract the total in part e from 2.500 V, then divide
the difference by two.
g.
ADJUST— DAC Ref (R2127 on the Control Board) to
add the (signed) number obtained in part f to the reading
obtained in part d.
5-7
Содержание 2445
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