Schematics V5.0

Listed below are schematic diagrams for many HP handheld and desktop calculator products. These diagrams were produced by dismantling and reverse-engineering the machines, and are not endorsed or supported by Hewlett-Packard in any way.

These diagrams are intended to aid electronically-knowledgable owners in repairing their machines. They are not intended as an introduction to calculator repair, and beginners will almost certainly need to refer to standard books on electronics before they can understand them. Also, many of the devices described here use lethal voltages (including the AC mains), and it is essential to know what you are doing and to take great care before attempting to repair such devices. If in doubt, ask before working on such machines.

These diagrams are offered in good faith, however it would be extremely surprising if there were no errors. Neither the author nor HPCC will be held liable for any loss or damage that results from using the information on this disk.

You can download the complete zip file of schematics for offline browsing.

DrARD 2015

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 included here.

Unless otherwise specified, these diagrams apply to UK versions of the machines. Voltage 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 containing 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 schematics 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 identified 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 un-terminated 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 obtained second-hand and had presumably been used previously) and ARD's wiring to general purpose connectors. 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.

Schematics