Acknowledgments and special thanks

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My many thanks go out to all of those who have helped me compile, formulate or present this book.

Tom Crider jrNEWSLETTER Magazine

Ed Strauss

E.S. Quality Products

John King

SAN FRANCISCO PCjr Users Group (Keep me straight John)

Carl Haub

METRO PCjr Users Group

THE ATLANTA PCjr Users Group

Tom Skladany and Crew AMERICAN SPEEDY PRINTING Columbus Ohio

(Printers Extraordinar)

The Groups from TEXAS,BOSTON and OHIO
My Very Supportive and Hard Working Family

IBM and IBM PC Junior are trademarks of the IBM Corporation.

MS and Microsoft Junior Booster are trademarks of the MICROSOFT Corporation.
TM, Tecmar Junior Captain and Junior Wave are trademarks of the TECMAR Corporation.


Thank you for purchasing PCjr Power. This book and the software is a compilation of more than a years work combined with six years of experience with the Junior, engineers, users groups and Juniors owners. The PC Junior is a great piece of computer architecture and it enjoys one of the top spots among a host of computer hardware. Rightfully so.

PC Junior owners have been a constant source of inventive information when attempting to overcome the design problems thought to limit the Juniors ability. I have just scratched the surface in the compilation of helpful items within this book, but I certainly hope this information is helpful to both the novice and experienced users who have constantly sought to upgrade their great little computers.

Continue to seek excellence,
Albert L. Allen President Owl Software

Printed 1989 Copyright (C) 1989 by Owl Software Albert L. Allen



Connector Port Layout 1

Keyboard Routines 3

Parts and Part Numbers 5
Understanding DOS 6

Autoexec and Configuration Files 17

The Command Interpreter 20

Using DOS 3.2 and 3.3 22

Replacing Disk Drives 24

256K Chip Handling 25

Cure for Monitor Smearing 26

Communications Hints 27

Curing Noisy Disk Drives 29

Cleaning the Disk Drive 31

Tecmar Memory Overheating 31

Damaged Rear Connectors 32

Static/Errant Electrical Charges 32

Speeding Up the Junior 33

Hardware Sources 34

Monthly Newsletter Available 34


Using 736K Through Sidecar Modification 36

Adding a Reset Button 37

Tandy 1000 Upgrade 39

Adding a Second Disk Drive 40

Disk Controller Card Modification 41

Making a Two Drive Cable 47

512K IBM Sidecar Upgrade 49

512K Microsoft Upgrade 53

V20 Chip Addition 56

DOS 2.1 60

Arctic Fox 62

Newsroom 63

Print Master 64

Print Shop 64

Ancient Art of War 65

Electric Desk 66

Writing Assistant 67

Filing Assistant 68

Reporting Assistant 69

Graphing Assistant 69

PFS File 70

PFS Report 71

PFS Write 72

Homeword 72

Enable 73

Tandy Modification Precautions Al

Building a Serial Port Card A2

A New Second Drive Controller Modification A7

Controller Modification for Three Drives A12

Two and Three Drive Cable Construction A15

Additional Parts and Part Numbers A19

PCjr Diagnostic Outline A20

Common PCjr Repair Problems A21

Additional Monitor Problems/Cures A23

Monitor Data A24

Software Patches A25

F-19, Kings Quest 4, Sierra

and Prodigy

Miscellaneous Information A29 Joy Port Info, Genius Mouse Use,

Higher Speeds for the Jr Captain,

Video Gate Array Problems, Checking

for a Speech Adapter, Cartridge Dump to Disk File

Additional Program Compatibility Listing A32


Owl Software is not responsible for any modification made to software or hardware from the contents of this book.



Starting in the front of the PCjr and located to the right beneath the disk drive there are two cartridge slots for ROM cartridges programs like BASIC, Lotus and many games. These slots are also used to house the many new third party configuration cartridges and ROM clocks. There is also a plug-in to double each slot space called a Siamese Slot which allows each single slot accept two cartridges.

The IR (infra-red) port which receives information from the keyboard is the 3/8" hole located just to the left of the cartridge ports. If you are using the standard PCjr keyboard you can put 4 AA batteries into it and access the computer without a physical cable attached from the keyboard to the computer. There is a keyboard adapter which will replace the IR internal detector. This adapter will allow a PC-XT style 84 or 101 key keyboard to be used with the Junior and will also provide a keystroke buffer which will accept input while other functions are being processed by the CPU.

On the right side of the computer under a snap off side cover is located a 60 pin buss connector which is used to attach a great deal of items. These include memory expansion, parallel printer port, power attachment and some hard drives. Caution should be observed when you use this port, and you should avoid touching the pin area as static shock could ruin your system board. If you attach more than two sidecars a extra power supply module should also be added to provide adequate power.

Facing the rear of the computer you will notice six connectors on the left side labeled J,J,L,K,LP and T. The two "J" connectors are for joysticks, left and right. The standard PCjr joystick will fit these connectors. Also there is an adapter available to use a standard PC joystick with either of these connectors. The "L" connector is listed as a spare and I don't know of a use for it. The "K" connector is the standard plug-in for the keyboard cable. The "LP"

connector was originally for light pen use, but it is also used in conjunction with the "K" port for an adapter which allows the connection of a PX-XT style keyboard. The "T" port is used plug in the television adapter which allows use of a TV for a monitor. This port can also be used to adapt a single color TTL monitor to the Junior.

The circular connector labeled "V" in the middle of the back is the the COMPOSITE video port. You can plug a single color composite monitor into this. Above this port is the square connector labeled "M" which is the modem output connection to the telephone line.

The next set of connectors to the right are labeled D,S, and C. The "D" port is the RGB color monitor output. You can use the PCjr color monitor or you can use any standard RGB color monitor with a COLOR ADAPTER CABLE which will allow you to attach it to the "D" port. The "S" connector is the serial port used to attach many items such as a serial printer, mouse, external modem and other serial peripherals. You will need a SERIAL ADAPTER CABLE to adapt the industry standard 25 pin D connectors to the "S" port. The "C" connector is used for cassette recorder storage. With a disk drive this is virtually a unused port.

To the right is the last circular connector labeled with a "A" for audio output. The remaining rectangular connector labeled PWR is the power input to the computer from the external 16.7 volt transformer.


The standard 1/2 height, 5.25" floppy drive inserted into the PCjr consist of;
2 Heads (1 per side)

40 Tracks(cylinders) per side 9 Sectors per track

512 Bytes per sector
The head settle time is 21 milliseconds, motor start is 500 milliseconds. Head load time is not applicable. The unit is BELT driven, and the heads ride on plastic bushings.

The PCjr keyboard is a very unique input device with many routines that emulate the larger PC XT style keyboards and some routines that the larger keyboards do not have. It is important to know your way around the Junior keyboard.

Starting with the Function Keys, the "FN" key in the upper right corner is a STICKY key. This means that when it is pressed it can be released and the next key in the sequence can be pressed without having to hold down the FN key.

To obtain the F1-F1O keys press the FN key and the appropriate number key, 1-0.

To cause a Control Break which ends most programs running in either DOS or BASIC press FN + B (break).
To cause the screen print to Echo to the printer press the FN + E (echo). Everything typed after this command is invoked will print to both the screen and printer. Issue the command again to turn it off.

To Print The Screen contents on the printer press the FN + P (print screen). Make sure the printer is turned on. This is the same command as Shift Print/Screen on the PC XT style keyboards. This will print the 25 lines of screen information that is on the monitor at present.

To Pause a program execution or a scrolling screen, press the FN + Q (pause).
To cause the keyboard to enter the Number Lock Mode you must press and hold the ALTERNATE key then press the FN key then the N key, ALT+FN+N (number lock). Then you can enter any of the 256 ASCII codes by pressing and holding the ALT key along with the ASCII code. When you release the ALT key the character will appear on the screen. For example character 143 will cause most printers to enter the compressed print mode. Echo the keyboard (FN+E) then enter the number lock mode and hold down the ALT key and type 143. A small character will appear on the screen and everything sent to the printer after that will be in the compressed print mode until a reset code is sent or the printer is turned off and back on again. To leave the number lock mode press ALT+FN+N again.
To Reboot (restart) the computer on what is called a warm boot, press CONTROL + ALTERNATE + DELETE keys all together at the same time, CNTL+ALT+DEL (reboot).
To move the Screen Alignment Left or Right press CONTROL + ALTERNATE + either the LEFT or RIGHT ARROW keys.
To enter the PCjr Internal Test Mode, press CONTROL + ALTERNATE + INSERT keys at the same time. Diagnostics will begin from the PCjr internal ROM storage. CNTL+ALT+INS (test mode).
To begin Keyboard Click which issues a sound when you press each key, press CONTROL + ALTERNATE + CAPS LOCK, CNTL+ALT+CAPS LOCK (keyboard click).

To enter the Function Lock Mode which makes the keys 1-0, and the B,Q,P,E and S along with the cursor control keys function as though the FN key were pressed first, press the FN + SHIFT + ESC together. This same key combination will turn off the function lock mode. FN+SHFT+ESC (function lock mode)


The following is a list of the current parts and parts numbers associated with the PCjr computer. The prices noted are from Owl Software 1435 Burnley Sq. N. Columbus, Ohio 43229 and they are available for immediate shipment. Parts listed as EXCHANGE must have the old part returned to IBM within 30 days receipt of the new item or the full retail price is charged.



KEYBOARD 6135725 ($75.00)

KEYBOARD CORD 8285983 ($19.95)


POWER BOARD 6135986 ($44.00 Exchange)

64k MEMORY BOARD 8654227 ($80.00 Exchange)


INFRA-RED RECEIVER 8654226 ($22.95)

SYSTEM BOARD 8654225 ($137.00 Exchange)

DISKETTE DRIVE 8285997 ($89.00)

DRIVE SIGNAL CABLE 8285986 ($6.95)

DRIVE MOUNTING BRACKET 8286005 ($19.95) *Limited Qty

DRIVE FAN ASSEMBLY 8285982 ($29.00)

DRIVE CONTROLLER CARD 8284228 ($55.00)

PARALLEL PRINTER PORT 8285987 ($79.95)

TELEVISION ADAPTER 8285989 ($19.95)

PCjr JOYSTICK 8286002 ($27.95)

COLOR ADAPTER CABLE 8285991 ($26.95)

SERIAL ADAPTER CABLE 8285993 ($14.95)

All of these parts can still be purchased from IBM Parts Order if they cannot be found from your local PCjr dealers. Prices do not include shipping and are subject to change without notice.


I have taken the time to write this section for all of the computer owners who have troubled, haggled, queried or scratched their heads to get a BEGINNING GRASP of the DOS commands. This section is for any user of PC equipment including PC-XT, AT, Clone or PCjr. It is general in nature and the examples are common to all versions of the DOS language from version 2.0 on.

Remember that the key to mastering these basic techniques is to practice the examples and to envision how they will apply to the work that you have to achieve.
WHAT IS DOS? (Disk Operating System)
DOS is a program (software) that allows you to "talk" with the computer and its peripherals. For example, you talk through the keyboard to the CPU (central processing unit) to the screen, disk drives, printer, modem or monitor and etc. These items are called the computer (hardware).

DOS also contains the utility programs for diskette preparation, file organizing and other file manipulations on your diskettes. You give commands with regular words like FORMAT, DISKCOPY,. COPY, ERASE or PRINT and DOS carries these commands to the computer to complete the tasks.
There are two forms of DOS commands;

  1. INTERNAL COMMANDS - stay resident in the computer memory when DOS is started. Ie; (Copy and Dir)
  2. EXTERNAL COMMANDS - are program files which must be loaded from the DOS diskette each time you use them. In order to use a external command the DOS diskette must be in your disk drive or that program file must be on current diskette you are using. Ie; (Diskcopy and Format)

DOS has many versions and, as the version numbers increase so does the amount of RAM (random access memory) needed to contain the larger DOS programs. Some versions of DOS, like version 3.1 or 3.3, may cause noisy disk drive operation in some computers and special quieting programs are needed to run these disk drives at their normal speeds.
DOS can work much more efficiently with two physical disk drives. But for single disk drive systems, DOS is able to get around this problem by creating two LOGICAL disk drives. Your one physical drive acting as two drives.
In situations involving a single disk drive, DOS uses the same disk drive labels as it does in a two drive setup. The A drive is logical drive A, the B drive is logical drive B. The difference between the two examples is that in the single drive situation both labels refer to the same physical drive instead of two separate drives. When a command using both drive A and drive B is executed, DOS switches the label attached to the one drive as needed. Execution of the command is held up during each switch so that you can swap diskettes in the single drive.
The effect with single drives is that operation that require two diskettes like DISKCOPY, COPY or FORMAT, can be accomplished as though two physical disk drives were present.

With the computer turned off open the disk drive door on the computer and put your DOS diskette into drive A:. On most PC-XT, AT, or PCjr's the disk goes in with the label UP and the notched edge to the LEFT. Remember not to touch the diskette in its open section where you can see the magnetic film of the diskette. This will make the diskette unusable.

Close the disk drive door and turn your computer and monitor on. After your computer checks itself and counts the memory, the disk drive light will come on and the DOS program will start to load into the RAM memory. Usually DOS will clear the screen and you will see the following message;

Current date is Monday 01-01-80 (maybe any date) Enter new date (mm-dd-yy):_

The CURSOR will be positioned after the colon. (The cursor is the small blinking character that shows where the next character will be placed on the screen.)
You will need to enter the date using the format of month, day and year, Ie; 03-06-87 or 12-25-88. When you type in these characters the cursor moves along always one place ahead of the last character that you typed in. When you are finished typing in the date, DOS is waiting for you to give it a command to execute the order. You must strike the ENTER or RETURN key telling DOS to execute the command or function you just typed.
In this manual, anytime that you see;
it means to strike the ENTER or RETURN key and give DOS the (execute command.)
You will find that DOS requires the proper spelling and the correct syntax (order) to process your commands. You may make correction in the command line using the BACKSPACE or ARROW KEYS anytime before hitting .
The next message you will see is;
Current time is 06:05:30 (may be anytime) Enter new time:
The time format is; hours: minutes: seconds: hundredths of seconds. DOS uses military time or the 24 hour clock. For example 11 a.m. will be displayed as 1100 or 6 a.m. will be displayed as 0600, but 1 p.m. will be displayed as 1300 and 2 p.m. as 1400 and so on. So the afternoon hours will have 12 added to them. You may set the DOS clock by typing in the hours and minutes and you may add seconds as a option. If the actual time is 4:15 p.m. you would type in;
Enter new time:16:15

You will now see the version screen with the DOS prompt. The version screen shows the current version of DOS that you are using followed by the DOS prompt which indicates the current (DEFAULT) disk drive you are using;

The AAA Personal Computer **-DOS

Version 2.10 Copyright XXXXXX Corp. 1983, 1984


The cursor is positioned after the DOS prompt and DOS is now ready to accept your commands.

Congratulations, you have successfully loaded DOS into the computers memory. This process is also called "BOOTING" your computer. It is also called a "COLD BOOT" because you started with the power off to the computer. You may begin the process again in what is called a "WARM BOOT" by pressing and holding the CONTROL with the ALTERNATE and DELETE keys simultaneously and releasing them.
NOTE: You may simply strike at both the date and time prompt if you don't want to put in these items. If your computer has a clock and calendar board the correct date and time might be kept in the computer memory and you pass the date and time entry in the "boot" and come directly to the DOS prompt ready to enter commands.
On some computers your screen will be in the 40 column wide mode on boot up. Some Tandy and IBM PCjr's are this way. You can place the screen into the 80 column wide mode by typing;
A> MODE CO80 (for color monitors) or A> MODE 80 (for monochrome monitors)
MODE is a external DOS command so your DOS diskette should be in the disk drive to complete this procedure. NOTE: Your computer should be used from the 80 column mode to be compatible with the majority of business software which requires starting at the 80 column screen.

There are six commands that you must learn to use efficiently to start getting a grasp of DOS. These commands are DIRectory, DISKCOPY, FORMAT, COPY, TYPE and CHKDSK (Check Disk). We will cover these six commands next.

Now we are ready to start using DOS to communicate with the computer. Lets give DOS your first real command. At the A prompt type;

A>DIR What happened?

The disk drive light came on and a listing of the files contained on your DOS diskette appeared on the screen. You asked DOS to print a (DIR)ectory of the material contained on the diskette in the default disk drive. If your DOS diskette contained a lot of files the upper ones probably scrolled off of the screen before you had a chance to see them.

Let's try the DIR command again, but with a small addition;


This time the disk directory is displayed, but at the end of a full screen of file listings the computer stopped and asked you when you are ready to continue. You have used the (DIR)ectory command with the (P)age option.
Normally these type of options, placed after the command and used with a slash, are called SWITCHES. When the (P) option is used it is said that the (P)age switch is turned on.
There is another nice switch associated with the DIR command, try this one;
Notice that the disk directory this time was printed to the screen in the (W)ide fashion that covers the width of the screen. If a diskette directory is extremely large the two switches can be used together;
This command will produce a diskette directory in the wide style that will pause when the screen is full,
If you have two physical disk drives and you wanted to see the files contained on drive B, you can do either of two things;
A>B: this changes the default drive to drive B.
You may change between default drives as simply as indicated above. Just type in the drive letter FOLLOWED BY A COLON and hit enter. If you leave the colon off of the command string you will get a error message, le;
Bad command or file name A>

You can see that the syntax is VERY important, the computer needs the exact syntax to process you commands.

Notice that in the wide mode the DIR command does not print the file size or origin date and this save space on the screen or when printing out the directory to a printer. Try this DIR command with other diskettes and view their file directories. While we are discussing files maybe we should look at the importance of file names,

Files are every group of material stored on the diskette or in the computers memory. Some files may makeup the program that does the work while other files contain the work produced by the programs. These are called output files. An output file maybe a letter you have written with your word processor or a christmas card mailing list you have created with your database. Other files may contain instructions for operating a program these are called documentation files. The factor usually determining the nature of the file is the FILENAME EXTENSION, ie;
wordproc.doc The (DOC) extension indicates this file is documentation for the program.
database.txt This is a text (TXT) file probably containing instruction for the program called database.exe.



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