HP 82718A User manual

HP 82718A
Expansion Pod
Service Manual
WKSl HEWLETT
WmM PACKARD

m
HEWLETT
PACKARD
HP 82718A Expansion Pod
Service Manual
Reorder Number Printed In U.S.A.
82718-90006 ®/84

Contents
Section Page
1 Product Information
1-1 Introduction 1-1
1-2 Description 1-1
1-3 Specifications 1-2
1-4 Identification 1-2
2 Installation
2-1 Introduction 2-1
2-2 Preparation 2-1
2-3 Functional Verification 2-3
3 Functional Description
3-1 Introduction 3-1
3-2 The Memory Management IC (MEMIC, 1LH7) 3-1
3-3 ROM ICs : 3-2
3-4 Modem Controller Circuitry 3-2
3-5 Power Supply 3-2
3-6 Jumpers 3-3
4 Removal and Replacement
4-1 Introduction 4-1
4-2 Required Tools 4-1
4-3 Disassembly Procedure 4-1
4-4 To remove the power PCA: 4-2
4-5 To remove the modem PCA: 4-4
4-6 To remove the ROM connector: 4-4
4-7 Reassembly Procedure 4-4
4-8 To reassemble the ROM connector: 4-5
4-9 Td reassemble the power PCA: 4-6
5 Troubleshooting and Diagnostics
5-1 Introduction 5-1
5-2 Required Tools 5-2
5-3 Initial Preparation 5-2
5-4 Test Procedures 5-2
6 Replaceable Parts
6-1 Introduction 6-1
6-2 Ordering Information 6-1
7 Diagrams
7-1 Introduction 7-1
A Appendix A
A-1 Introduction A-1
B Appendix B
B-1 Introduction B-1

HP82718A „
Contents iii
Illustrations
Figure Title
2-1
2-2
2-3
3-1
End-Retainer Screws 2-1
HP-75 Installation 2-2
Batteries Installed in the Pod 2-2
HP 82718A Block Diagram 3.]^
4-1 Bottom-Case and End-Retainer Screws and Battery Compartment 4-2
4-2 "
4-3
4-4
4-5
Power-PCA Mounting Screws 4.2
Disconnecting the Modem Flex Cahle 4.3
ROM-Connector-Shield Screws 4.3
Modem PCA, Modular Jacks, andI/O Panel 4.4
4-6 ROM-Connector Cable Strain-Relief Bar and Connector 4-4
4-7 ROM-Connector Test Setup 4.5
4-8 Installing the ROM-connector Shield Screws 4-6
4-9. I/O-Panel Installation 4.3
4-10 Installingthe PCAs 4.7
4-11 Securing the ROM-Connector Shield 4.7
6"! HP
82718A Expansion Pod Exploded View 0.3
6-2 Component-Location Diagram 3.5
7-1 Power PCA, Electronic-Disc Schematic 7.3
"^"2 Power PCA, Modem-Interface Schematic 7.5
7-3 Power PCA, Power-Supply Schematic 7.7
Tables
Table Title Page
1-1 Specifications 3^.2
4-1 Required TdoIs 4.]^
5-1 Required Tools 5.2
5-2 The HP-75 Does Not
Tirn On 5.3
5-3 Power Supply Voltages 5.4
5-4 The HP-75 Tbrns On 5.4
6-1 Replaceable Parts,
Assembly Level 6-1
6-2 Replaceable Parts, Component-Level 6-4
A-1 Diagnostic Tfest Error Messages A-1

About This Manual—
This manual contains the information you will need to service the HP 82718A Expansion Pod.
You should read this manual through once completely before attempting any repairs, as some steps assume a
prior knowledge of other steps and cautions.
The manual contains the following seven sections:
• Section 1- Product Information. This section gives a general overview of the pod as well asits phys
ical and electrical specifications.
• Section 2 - Installation. This section tells how to prepare the pod for use and how to verify its func
tional operation.
• Section 3- Functional Description. This section gives a brief description of the functions ofthe major
blocks in the pod.
• Section 4 - Removal and Replacement. This section tells how to remove and replace pod assemblies.
Section 5 - Troubleshooting and Diagnostics. This section tells how to troubleshoot and repair the pod.
• Section 6 - Replaceable Parts. This section lists the replaceable parts and contains an exploded view
and component location diagram of the pod.
Section 7 - Diagrams. This section contains the schematic drawings of the pod.
Appendix Acontains component-level repair information, and appendix Bcontains listings of the
diagnostic ROM programs.
The tools and test equipment required to service the pod are listed in tables 4-1and 5-1 on pages 4-1 and
5-2 respectively.

Section 1
Product Information
1-1. Introduction
This section provides an overview of the HP 82718A Expansion Pod.
The podis a portable, battery-operated accessory forthe HP-75C/Dcomputer; it adds two enhancements
to the computerthat are valuable for RDDP (remotedata distributed processing) applications: an integral
direct-connect modem and extended memory.
1-2. Description
The 300 baud modem has the following features:
•Bell 103-compatible originate/answer.
• Two RJllC direct-connect jacks.
•Automatic reporting of call failure, commimications estabished, and loss of communications.
• Automatic call answering.
• Automatic disconnect on call failure or loss of communications.
• Automatic dialer (pulse, tone).
The modem is controlled by its own MPU (microprocessing unit) and associated circuitry. Low-level
modem commands are included in 4K bytes of ROM.
Up to 64K bytes of extended electronic disc memory can be installed inthe pod in increments of 8K bytes.
Standard configurations are 24K-, 32K-, and 64K hytes.
High-level modem and electronic-disc commands are included in 16K bjrtes of ROM that are identical to
the HP-75 plug-in ROMs.
The pod connects directly tothe HP-75 bus through the right-hand front ROM port and is controlled by a
memory-management IC (integrated circuit).
The two battery packs inthe pod provide power for both the pod and the HP-75. They can be recharged
by plugging an ac adapter into the HP-75 while it is installedin the pod.

1-2 Product Information
1-3. Specifications
Equipment specifications are shown in table 1-1.
Table 1-1. Specifications
Physical
• Dimensions (HP-75 plus pod): 29.2 cm by 16.5 cm by 6.4 cm (11.5" by 6.5" by 2.5")
•Weight
(HP-75 plus pod): 1.60 kilograms (56.5 ounces)
Electrical
• 175 milliamps (max) at 5.2 to 5.5 Vdc.
Environmental
• Operating temperature: 0 to +45°C (32° to 113°F).
• Storage temperature: -40° to -f-55°C (-40° to 131°F).
• Recharging temperature: -1-10° to -}-40°C (50° to 104°F).
HP 82718A
1-4. Identification
The serial number of the HP 82718A is used for identification and the determination of warranty status.
It is located on the bottom overlay. Its format is described below.
Y Y W W
n K
A
B
Q
S
X X X X X
Sequence number.
Location manufactured:
A=U.S.A.
Week manufactured -f 8.
Year manufactured
(Years since 1960)
Number of bytes of RAM installed.

Section 2
Installation
2-1. Introduction
This section tells you how to prepare your HP 82718A Expansion Podforuseand how to verify its func
tional operation.
2-2. Preparation
To prepare your pod for operation, do the following:
a. If the end retainersare in place, remove them by unscrewing the six long screws in the bottom case.
Figure 2-1. End Retainer Screws
b. Be sure the HP-75 is turned off.
c. Remove the battery pack from the HP-75.

2-2 Installation
HP 82718A
d. Install the HP-75 in the pod by plugging in the ROM connector, placing the HP-75 on the top case,
and installing the end retainers.
ROM Connector
Figure 2-2. HP-75 Installation
e. Install charged batteries and the battery door in the pod.
'
Figure 2-3. Batteries Installed in the Pod
f. Remove a dummy ROM if present from either of the other two ports in the HP-75 and install a pod
diagnostic ROM.

Installation 2-3
2-3. Functional Verification
Tb verify the functional operation of the pod, do the following:
a. Press Iattn I. The HP-75 should turn on. If it doesn't, go to table 5-2.
b. If the HP-75 turns on, go into the edit mode (press rEPirl). type in RUN "P" and press fWrNl. The
pod test program runs. (You will need to press I EDIT I twice if this isa cold start.)
c. If the unit is good, various messages are displayed, and then "pod OK (nn)" is displayed, where nn
corresponds to the number ofK bytes of installed RAM as indicated on the pod label. In case an error
message is displayed, refer to section 5 for analysis of the results.