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First Jr.

PostPosted: Sun Mar 31, 2013 12:36 am
by OffensiveJerk
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So I normally don't post in the intro forums, but I figured this is a fairly specialized forum dedicated to one machine, so why not?

Anyway, I have been hankering a jr for a while, just because it seemed so odd. Also, the graphics and sound are way better than my other IBM's with CGA and Mono graphics. I also liked the joysticks. After looking for a while, I just picked up a jr of my own locally. The gentleman had it boxed up since 1992.

It's a 4860-004 model with 128k total RAM. It came with 2 joysticks, a keyboard (second revision), and the Jr. monitor. There was also a box of books and software.

-Adventure in Serenia
-Math Maze
-Scuba Venture
-Home Budget, Jr.
-Touchdown Football
-Mine Shaft
-DOS version 2.10 (no software :( )
-BASIC Personal Computer PCjr ( did that ever come with disks? There is a insert for disks in the manual)
-Your IBM JR Software Sampler

-Hands on Basic
-IBM PCjr Software Guide and Handbook
-Guide to Operations

I would still like to get some accessories with it eventually such as the parallel port, and a jrIDE, probably an ethernet card.

There are some issues with it, however. The keyboard was corroded from battery storage, but I did manage to save it. There seem to be issues with the floppy drive. It does seem to read disks reliably. I did clean the heads with a cleaning disk, and also cleaned and lubed the rails, but the issues remain. It seems to read worse the longer it's used. Just for kicks I made a boot disk on my DOS 6.22 machine, and tried to boot it. At first it would try to boot, but then garbage would spit on the screen and it would lock up. After a few more tries, it just doesn't try to boot it anymore. I couldn't get it to boot a DOS 2.1 disk I had made previously. I don't have much hope for this drive anymore.

Also, I put the Home Budget Jr, software disk in my IBM XT and now there are score marks all over the disk, and it fails to read. This computer never had an issue with ruining disks before, so I don't know what's going on. I read some older posts on here about testing the drive speed, but if it's a belt issue, can those even be sourced? Anyway, some pics.

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Re: First Jr.

PostPosted: Sun Mar 31, 2013 9:06 am
by Brutman
Hello, and welcome to our elite little club.

That is a reasonable selection of software that shows the capabilities of the machine fairly well. We can help you with the DOS 2.1 diskettes - that should be a 2 diskette set (160KB each) but it is more convenient to just use one 360KB disk. The BASIC reference manual came with the BASIC cartridge ("Cartridge BASIC") which is needed to expose the advanced capabilities of the machine from BASIC. You can still use BASIC without the cartridge, but it takes a little cheating to get it to work. (Rename the DOS versions of BASIC.COM and BASICA.COM to something else, like DBASIC.COM and DBASICA.COM.)

If your machine really only has 128K then the jrIDE is a great upgrade. You need more memory, and you might as well get an IDE interface too. A parallel port is a must too - that allows for Zip drives and the Xircom PE3-10BT Ethernet adapter. Oh, and parallel printers of course. ; - 0

I have some keyboard circuit board pictures for you to help you repair/diagnose yours. Corrosion problems are nasty, but those circuit boards are crude enough where repairs are very feasible.

DOS 6.22 will not boot directly without patching it. DOS 2.1 should be fine, so just clean the drive again and hope it is just a dirty head problem. I start by cleaning the rails with q-tips soaked in nearly pure isopropyl alcohol. (Look for 91% or better - it's cheap.) Do not double dip and contaminate the alcohol source. I then use a light machine oil with a q-tip to spread the oil lightly across the rails, sliding the head assembly back and forth a few times to spread the oil too. The heads can be cleaned with a clean q-tip and alcohol, but be extremely careful not to knock them out of alignment. Doing so is probably fatal - see below.

On the XT floppy drive - if you knocked the heads out of alignment when cleaning them then the heads might be digging the diskettes up. Don't put any more diskettes in there unless you can afford to lose them. Verify that it really is the heads dragging on the diskettes by looking to see if the heads are protruding down at a bizarre angle, or by trying a known good diskette that you won't need again. If the drive digs the surface again you need another drive, unless you can figure out how to fix that one.