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Maintenance— 2440 Service
Table 6-6 (cont)
Using the CH 2 probe:
6.
Check each address line in order (from AF to AO) for a valid TTL-level signal, with each lower
address line having a frequency of exactly twice the frequency as the address above it. Any loss
of the 50% duty cycle and/or distortion indicates a shorted address line. Check both the input and
output pins of Address Buffers U732 and U632 to verify that they are working correctly, and to
determine if address lines are shorted after the buffers. Waveform numbers 6, 7, 8, 9, 10, and 11
on schematic diagram 1 may be used to compare against the observed waveforms.
7.
If a fault is found, if may be necessary to isolate the System
i*P
address bus from the Waveform
nP
address bus to determine what circuitry is causing the problem. See the BUS ISOLATE and
the W AVEFORM
tiP
KERNEL MODE procedures following the SYSTEM
fiP
CHIP SELECT TEST.
System
nP
Chip-Select Test:
1.
From the Kernel mode, momentarily short the pins of J129 together to reset the processor. This
forces ROMO.O to be switched in. Set the test scope to 10 ms/div to view one whole cycle of the
AF period, and set the Trigger Slope so that AF is shown LO during the first half of the display.
While AF is LO, addresses from OOOOh to 7FFFh are being executed; while HI, addresses from
8000h to FFFFh are executed.
2.
Move jumper J127 (shown on schematic diagram 2) to connect pins 2 and 4. This causes the
“ BUSTAKE” condition so that the System
nP
has access to the Waveform
nP
memory space. In
this mode, most of the processing system can be verified.
Using the CH 2 probe:
3.
Look for a LO chip-select signal, at the point designated in the following table, that occurs during
the correct portion of the AF waveform period. Waveforms 20, 21, 22, 23, 24, and 25, may be
used as comparison waveforms for the chip selects output from Address Decoder U570
(schematic diagram 2 — Waveform *iP).
Chip
Select
Test
Point
Bus
Address
Range (hex)
Position Within
the AF Period
SAVE
U580-8
W P
0000-1FFF
First 1/8th
DISP
U570-13
W P
2000-2FFF
Third 1/16th
DATT
U570-12
W P
3000-3FFF
Fourth 1/16th
ACQ
U570-11
W P
4000-4FFF
Fifth 1/16th
C M D/TEM P
U250-8
W P
5000-57FF
Twelfth 1/32nd
COEFF
U250-11
W P
5800-5FFF
Thirteenth 1/32nd
H M M IO
U870-6
BOTH
6000-6FFF
Seventh 1/16th
NVRAM
U840-6
SYS
7000-77FF
Sixteenth 1/32nd
SYSRAM
U840-3
SYS
7800-7FFF
Seventeenth 1/32nd
ROMO.X
U890-4
SYS
8000-BFFF
Third 1/4th
ROM1
U890-5
SYS
C000-FFFF
Last 1/4th
6-100
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 ...
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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 432: ...2440 Service WAVEFORMS FOR DIAGRAM 2 BUS ISOLATED 6 6 0 3 4 9 ...
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Page 517: ...10 16 R E V J U L 1993 Replaceable Mechanical Parts ...
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