Maintenance— 2440 Service
Table 6-6 (cont)
GPIB
GPIB Test for Activity (schematic diagram 20):
1.
Press the O U TPU T menu button, then SETUP, then MODE. Select L/ONLY and see if the ADDR
LED is on. Select T /L and see if the ADDR LED is off. Select T/ONLY and see if the ADDR again
is on.
2. If the LEDs follow the above, GPIB 1C U630 is at least responding to the System
nP,
and the
problem is probably in GPIB Bus Buffers U 720 or U624.
3.
If the LEDs do not follow the above pattern, troubleshoot bidirectional buffer U532 or U630
(assuming the LEDs do the 0 through 7 binary count during REG test section of EXT DIAG).
FRONT PANEL
Front Panel and Auxiliary Front Panel (schematic diagrams 4 and 6):
PROBLEMS
If there is a front panel problem and the Extended Diagnostics have not detected anything, the prob
lem is not in the Front Panel Processor or its handshake logic with the System
nP.
On the Front Panel
nP
(U700), do the following checks:
N O TE
When probing around the Front Panel /.iP circuitry, it is possible to cause bad data to be
written to the System /tP and/or the Front Panel jtP by inadvertent grounding o f pins o r
accidental shorting o f pins together. If this should occur, m any trouble symptoms m ay be
present. To cure these symptoms, turn o ff the scope and turn it on again. This rewrites all
R A M space in the System and Front Panel microprocessors with correct operating data.
1.
Check pins 26, 27, 28, 29, 30, and 15 for active output signal switching. These signals are all
asynchronous, so a stable display pattern is not possible (without going to SAVE mode on the test
scope).
2.
If the signals checked in Step 1 are active, go to Step 3. If these signals are not actively switching,
perform the Front Panel M U XTEST to check that the
nP
drives the MUXSEL signal lines in a tight
looping routine. In the MUXTEST, only the MUXSEL signal output lines are being driven. No out
put will be seen on the S7C or SHCLK lines (pins 29 and 30 respectively).
3.
Check pin 24 for active AOUTO return signal from the Front Panel pots.
4.
If the return signal line is active, go to Step 5. If it is not active, showing the different voltage lev
els from the Front Panel pots, troubleshoot Front Panel Pot Scanner U902 (an 8-to-1 multiplexer).
Problems with a single pot output rather that a total failure of the Pot Scanner may be checked
out using the M U XTEST mentioned in Step 2.
5.
Check pin 25 for active return signal from the Front-Panel Switches.
6.
If the SW /O UT signal line is active, the Switch Scanner circuitry is working. If it is not active,
troubleshoot 1-of-8 decoder U903 and serial shift register U904 for correct operation.
7.
Check pin 22 (AOUT2) for an active return signal from the Auxiliary Front Panel INTENSITY pot
and Front Panel BNC connectors. Individual signal voltage levels may be checked using the Front
Panel M U XTEST if the signal line is active. If switching levels are not present on the AOUT2 signal
line, troubleshoot 8-to-1 multiplexer U600.
8.
Check pin 9 (SW OUTA) for an active signal when one of the Auxiliary Front Panel buttons is
pressed (bezel, SELECT, STATUS, MENU OFF). Otherwise, a HI is being shifted out of serial shift
register U700. If the SW OUTA signal does not show a square pulse when one of the buttons is
pressed, troubleshoot U700.
6-40
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 ...
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Page 455: ...W A V EFO R M S FOR D IAG RAM 11 WAVEFORMS FOR DIAGRAM 11 6603 29 ...
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Page 517: ...10 16 R E V J U L 1993 Replaceable Mechanical Parts ...
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