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Adjustment Procedure— 2440 Service
horizontally align its rising edge to center screen.
Position the top of the waveform to 3.5 divisions
below center graticule. Push ACQUIRE and set
ENVELOPE to CONTinuous. Check that the vertical
width of the trace between 5 ns and 15 ns after the
step transition is less than 0.4 division. (Push MENU
OFF/EXTENDED FUNCTIONS to turn off menu so
the waveform can be easily seen.) Set A SEC/DIV to
500 ns. Push ACQUIRE and set back to NORMAL.
4. Fine-adjust CM counts:
If both LF-linearity
checks in subpart 2, as well as the position-effect
check in subpart 3, were passed, skip to subpart 5.
If either of the LF-linearity checks
and
the position-
effect check failed, refer the instrument to qualified
service personnel for repair. Otherwise, display the
menu for adjusting the CM counts: Push MENU
OFF/EXTENDED FUNCTIONS twice; then SPECIAL;
then push FORCE DAC. Then, do the following:
• If either of the LF-linearity checks failed but
the position-effect check passed, rotate the
INTENSITY control to reduce CM 2E by
about 150 counts; then push W RITE TO
CALSTORE; then push the A HORIZONTAL
MODE front-panel button. Next, push the
downward arrow menu button to display
C M 2 0 and reduce it by about 150 counts
also; then push W RITE TO CALSTORE, fol
lowed by the A HORIZONTAL M O DE but
ton.
• If only position-effect check failed, repeat
C M 2 E /C M 2 0 adjustments as just described
for the LF-linearity check failure except
increase, rather than reduce, C M 2E and
C M 2 0 by about 150 counts.
If you had to reduce/increase the CM counts,
change the SEC/DIV setting to 200 ns and set
C M 2 0 and C M 2E to the new values just set for the
500 ns setting. Switch to 100 ns and repeat. (Use
the two left-most menu buttons to select between
C M 2 0 and CM2E; remember to always push W RITE
TO CALSTORE, followed by the A HORIZONTAL
MODE button after adjusting any CM count.) When
finished, return the SEC/DIV setting to 50
ns
and
repeat subparts 2, 3, and 4 until the LF-linearity and
position-effect checks pass or until CM count is
below 1500. (Always match the CM counts at
200 and 100 ns when they are changed at 500 ns.) If
any CM count must be reduced below 1500, the
instrument should be referred to qualified service
personnel for repair.
5.
GN-DAC counts check:
SEC/DIV should be
set to 500 ns. Push MENU OFF/EXTENDED FUNC
TIONS twice; then SPECIAL; then CCD ADJ. Push
ADJ Tl A2 to display the GN-DAC counts. ("TE S T
ING CHANNEL 2* should be displayed.) Check that
the GN-DAC counts for all four sides (1-4) are within
1000-3200. If one or more GN-DAC counts are out
side this range, change test-selectable resistors
R690 and R881 (located on Time Base board) to one
of the three pairs of values given in Table 5-1.
Resis
tors must be changed as a pair.
If the out-of-limit
GN-DAC counts are greater than 3200, increase
R690 and R881 to next higher pair of values listed; if
the GN-DAC counts are less than 1000, decrease
the resistors to the next lower pair of values.
Recheck GN-DAC counts and increase/decrease
resistors to the next pair in table as required. If GN-
DAC counts cannot be brought to within limits with
values pairs given in Table 5-1, refer instrument to
qualified service personnel for repair.
Table 5-1
Test Selectable Resistor Values
_______ (R690 and R881)
R690
PART NUMBER
R881
PART NUMBER
100 0
321-0097-00
301 0
321-0143-00
107 0
321-0100-00
348 0
321-0149-00
110 0
321-0101-00
374 0
321-0152-00
6.
Check LF-linearity and position effect, and
fine-adjust CM counts for CH 1:
Push the ADJ Tl
A2 menu button to turn off the GN-DAC counts
display. Set the SEC/DIV to 50
fis.
Move the 50-0
cable at CH 2 to the CH 1 input connector. Push
VERTICAL MODE, set CH 2 off and CH 1 on in the
menu. Adjust the generator for exactly 2 vertical divi
sions (discount trace width) amplitude, vertically cen
tered on screen. Now do subparts 2-5, using CH 1
controls instead of CH 2 controls and adjusting
C M IO /C M IE where C M 2 0 /C M 2 E are indicated.
("TESTING CHANNEL 1* will be displayed when
subpart 5 is performed.) Any time R609 and R881
must be changed to bring either channel's GN-DAC
counts within limits, subpart 5 must be reperformed
for the other channel. If the resistors must be
changed to a higher pair of values for one channel,
only to require a lower pair for the other channel, or
if both channels cannot be brought to within the
GN-DAC count limits, refer this instrument to
qualified service personnel for repair.
7.
Remove setup:
Push ACQUIRE and set
REPET O N !O FF to OFF. Disconnect the cable from
the CH 1 input connector.
5-1 0
REV SEP 1988
Summary of Contents for 2440
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Page 91: ...Theory of Operation 2440 Service 3 49 Figure 3 5 Simplified CCD architecture ...
Page 120: ...Theory of Operation 2440 Service Figure 3 10 DC Restorer 3 78 ...
Page 130: ...Theory of Operation 2440 Service 3 88 ...
Page 136: ...Theory of Operation 2440 Service Figure 3 15 PWM Regulator and Inverter 3 94 ...
Page 138: ...Theory of Operation 2440 Service Figure 3 16 PWM switching waveforms 3 96 ...
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Page 423: ...2440 Service Figure 9 4b 2440 Block diagram part 2 6330 27 BLOCK DIAGRAM PART 2 ...
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Page 428: ...2440 Service WAVEFORMS FOR DIAGRAM 1 6 2 8 5 3 2 ...
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Page 432: ...2440 Service WAVEFORMS FOR DIAGRAM 2 BUS ISOLATED 6 6 0 3 4 9 ...
Page 433: ...WAVEFORMS FOR DIAGRAM 2 ...
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Page 450: ...2440 Service WAVEFORMS FOR DIAGRAM 8 6603 27 ...
Page 455: ...W A V EFO R M S FOR D IAG RAM 11 WAVEFORMS FOR DIAGRAM 11 6603 29 ...
Page 458: ...WAVEFORMS FOR DIAGRAM 12 ...
Page 463: ...WAVEFORMS FOR DIAGRAM 14 ...
Page 471: ... C N i u i t e x r 4 j u J l i 1 i 6 28 5 44 WAVEFORMS FOR DIAGRAM 18 ...
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Page 502: ...2440 Service FIG 1 C A B IN E T ...
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Page 510: ...2440 Service SISSVHO Z Old ...
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Page 512: ...A12 2440 Service F IG 3 C IR C U IT BOARDS ...
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Page 517: ...10 16 R E V J U L 1993 Replaceable Mechanical Parts ...
Page 518: ...2440 Service ...
Page 519: ...FIG 4 L V H V PWR SUPPLY ...
Page 520: ...FIG 5 ACCESSORIES 2440 Service ...
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