Notes on particular machines and diagrams
-----------------------------------------

General
-------
In many cases IC power connections and decoupling capacitors are not 
shown on the diagrams.

`Obvious' cable wiring diagrams, such as straight-through ribbon cables, 
mains leads, and the like, are not inclucded here.

Unless otherwise specified, these diagrams apply to UK versions of the 
machines. Votlage selectors are shown set to the 240V position, the mains 
fuse shown is that for 240V mains.

In some cases, particularly in power supply and tape drive circuits, 
`select on test' resistors were used to compensate for tolerances 
elsewhere in the machine. The values shown were those present in the 
particular machine which was used for producing these diagrams.

HP9815
------
Two versions of the CPU board have been seen in these machines : the older 
one using 2102 RAMs and 2K byte ROMs (which can take a memory expansion 
card on top of the board at the rear); the later one using 2114 RAMs and 
8K byte ROMs. Schematics of both are included.

HP9820
-------
This machine has many PCBs in common with the HP910. The HP9820 
schematics only cover those parts that are unique to this machine -- the 
keyboard, display, memory box and I/O backplane. For all other sections, 
refer to the HP9810 diagrams. The first page of the 9820 diagrams 
explains this in more detail.

HP9830
------
The CPU in this machine consists of the same 4 boards that are used in 
the HP9810, which is why these pages have the latter's model number in 
the title. 

HP80
----
Two versions of the logic board have been found, the earlier one uses a 
hybrid circuit contianing 7 ROM chips, the later one uses 2 DIL-packaged 
`Quad ROMs'. Schematics for both are included.

HP87, HP87XM
------------
The only difference between these machines is the Logic 1 PCB. The other 
PCB scheamtics apply to both machines

Spice Series (HP31E, HP32E, HP33E, HP33C, HP34C, HP37E, HP38E, HP38C)
---------------------------------------------------------------------
These machines follow one of 2 basic schematics, one for the -E models, 
the other for the -C models. The memory and processor chips, and the 
keyboard layout, are of course different between the various machines in 
this family, but the connections between them, and the power supply board 
schematic is the same. This disk contains the HP32E and HP33C schematics 
as being representative of these machines.

HP10
----
This machine has 5 preset potentiometers on the logic board. These are 
indentified as VR1...VR5 on the schematic, they are numbered from the left 
side of the machine

HP11202, HP11203, HP98133, HP98134 interfaces
---------------------------------------------
These interfaces were originally supplied with an unterminated device 
cable, which was intended to be wired by the user to suit their device. 
The diagrams on this disk show the cables 'as found' (since the 
interfaces were obtaineqd second-hand and had presumanly been used 
previously) and ARD's wiring to general purpose conenctors. Neither is 
likely to match the wiring of other examples of these interfaces.

HP9144
------
This tape drive exists in at least 5 versions having 1..5 PCBs (+ PSU and 
front panel). These diagrams cover the 3-board (SBCont + Read/Write + 
Servo) and 1-board (Logic) versions. Others may be added if I obtain them

HPIB Disk and Tape units
------------------------
Various PSUs and fans have been used in these units. Each set of diagrams 
includes the PSU(s) and Fan(s) that have been found in the particular 
device. However, if your PSU is not shown, it is worth checking other disk 
or tape drives.
