Shadow Pca Elimination; Power Supply Changes; Disc Drive Assembly Changes - HP Integral Personal Computer Service Manual

11·2
P~uct
Hlatory
11.2.3 Shadow PCA Elimination
Early versions of the display assembly may have a small peA installed on the back of the assembly.
This is the ·shadow PCA."' It contains circuitry to prevent ·shadows· from appearing on the display.
This peA has been eliminated in the current display assembly since the shadow
circuitry
has been
added to the display assembly main PCA. The two versions of the odisplay assembly are interchange-
able. When replacing the display assembly, order the current assembly listed in chapter 9. For further
information concerning this change, refer to Service Note 9807 A-6.
Note. Do not remove the shadow peA from a display assembly that has it, nor transfer the
shadow PCA to a replacement display assembly that does not have it. Replace the entire dis-
play assembly with an exchange assembly. The display assembly is a
tuned assembly.
It cannot
be serviced to the component level in the field.
11.2.4 Power Supply Changes
Some minor component changes have been made to the power supply. Use the current replacement
components (listed in chapter 9) for all power supply repairs. If you replace the power supply, use the
current replacement PCA number listed in chapter 9. For additional information, refer to Service Notes
9807-2 and 9807-3.
11.2.5 Disc Drive Assembly Changes
The current 3 t h-inch disc drive assembly has a modified drive electronics PCA. However, the changes
are internal to the assembly, and the new assembly is interchangeable with the original one. Order the
current assembly (listed in chapter 9) whenever replacing a disc drive.
11.2.6 New Plug-In ROM A •• embly
Current production units come equipped with the HP 82995A ROM Assembly, which contains the
System V operating system. Earlier computers were equipped with the System III operating system,
but may be upgraded to System V by installing the HP 82991A System V ROM Upgrade Kit. All
System V ROM assemblies can be serviced to the component level.
If you are servicing a unit equipped with System III and the diagnostic tests indicate a ROM failure,
replace the ROM assembly. The replacement System III ROM assembly is part number
00095-60937.
When you replace the System III ROM assembly, you should also replace the plastic ROM cover
0(00095-40043),