IBM XT-286 Mechanic Required...

[Iain]

After some weeks quite happily using my renovated XT-286 I thought I'd make a slight modification to the unit and add another floppy drive. It currently has a 5.25" half-height floppy drive and I wanted to add a 3.5" drive in the empty bay beneath the 5.25" drive.

After locating a black 5.25 to 3.5" adapter tray, and then buying a 3.5" floppy drive with a black bezel (to match the front of the existing floppy and hard drives) I set about getting access to the lower drive bay.

This is where the problems began. I've swapped and fitted many 3.5 and 5.25" floppy drives in numerous computers, usually with very little difficulty. Most are simply screwed in a bay or attached via sliders. However, in the case of the XT-286 the 5.25" drive appears to be attached to a frame in the lower bay by a side panel, and the frame is held in place by a screw accessible through a hole in the base of the computer. Removing the base screw, then a screw on the side attaching it to a fixed panel, allows the the combined upper drive and lower frame to move slightly.

I have included a picture showing the combined drive and frame moved forward, protruding from the front of the machine. The drive is now wedged in this position and will not move any further forward. Even if it could move any further forward a small horizontal metal panel (seen partially covering some coloured wires going to a connector on the top of the drive) would come into contact with components on the drive's circuit board. Neither can the drive be removed in the other direction because the front bezel is larger than the opening in the drive bay. Perhaps the hard disk has to be removed to get access to screws that would allow the 5.25" drive to be seperated from the frame underneath it?

Rather than experiment and risk damaging the unit I thought I'd run the problem past the massed experience of this forum, some of whom may have encountered this problem before (or have an IBM manual where the dismantling procedure is revealed!).

-- Iain

 

[Terry Yager]

Looks like it should just slide right out. Hard to tell from the picture what it's catching on.

--T

 

[Micom 2000]

Sometimes there are hidden catches to restrict movement. Have you tried removing the Bezel ?

Lawrence

 

[Iain]

IBM XT-286 Mechanic Required...

Terry and Lawrence, thank you for your comments.

There are two bezels, one for the 5.25" drive and one on the frame below it. I cannot imagine the bezel on the 5.25" drive would need removing as this would call for somehow disconnecting the head lowering lever. I can see no way of removing the bezel from the lower frame.

However, even if both bezels were removed the drive could not be slid further forward because the small horizontal metal bar, part of the PC bodywork, would come into contact with the components on the drive's circuit board.

I can only presume that somehow the lower frame must be detachable from the drive. The frame could then come forward and be removed, which would allow the 5.25" dive to be lowered. This assumes that something could be done to overcome the way it becomes wedged in when moved forward a couple of inches.

It is hard to believe that anyone could come up with such a convoluted design for securing a floppy drive!

-- Iain

 

[Micom 2000]

Generally I've found IBM engineering and design to be excellent. Sometimes tho the retaining apparatus is not necessarily intuitive and I've had to search for it. Of course IBM techs would have the simplified and detailed maintenance procedures to go by. They are usually so detailed that even a complete novice would have no problem. Always made me wonder about the competance and training of IBM Techs. You used to be able to access the maintenance manual and I believe I even downloaded a few. After years of fiddling and upgrading I don't have a clue on which hard drive any of them still remain.
The earlier retaining clips were usually metal, the later ones plastic. The fact that it slid forward a bit might mean that it allowed you to access a screw or retaining clip.

Lawrence

 

[carlsson]

Generally I've found IBM engineering and design to be excellent.

Except for some PS/2 models (I can't recall which) that had plastic clips for the 72-pin SIMM slots. Ten years after production, they have dried and become fragile. *snap* On the other hand, it is the only really bad IBM experience I can remember, but I never worked intensively with them.

 

[Iain]

IBM XT-286 Mechanic Required...

In general I would agree with you Lawrence; which is why it is all the more strange that a company that had such a good reputation for its computer design should produce some construction that is so far from intuitive.

It may be one of those situations that after seeing the process done once it is obvious how it should have been done, but in the mean time if someone can point me in the direction of an on-line XT-286 maintenance manual it would be greatly appreciated.

-- Iain

 

[Micom 2000]

Well I have over a dozen PS/1 and PS/2s as well as a bunch of IBM Simms acquired on E-Pay. Thanks for the "heads-up". Never noticed the quality of the SIMMs.
I'll have to be aware, altho I must admit not having used most of them for a while. "Too many computers, too little time". I find a lot of my time used keeping my newer boxes functional or reacquainting myself with some platforms I'm getting rid of.

Lawrence

Except for some PS/2 models (I can't recall which) that had plastic clips for the 72-pin SIMM slots. Ten years after production, they have dried and become fragile. *snap* On the other hand, it is the only really bad IBM experience I can remember, but I never worked intensively with them.

 

[carlsson]

The SIMMs themselves are not the problem, the slots they go into. I solved it with a bit of adhesive tape across all four (?) SIMMs installed when I juggled around memory for best utilization. The tape attached to the other side of the power supply, and although I realize it would become loose after a while, it could be redone once the modules fall out of the sockets.

 

[Iain]

IBM XT-286 Mechanic Required...

Well, I managed to track down an IBM XT-286 Mechanic. A very helpful gentleman by the name of Jim Forbes, who happens to host a site dealing with vintage computers (amongst other things) called the 'Selectric Typwriter Museum' ( http://www.selectric.org/computer.html ).

After removing the screw in the base, then the screw in the side of the drive, it was possible to move the assembly a little way forward. The trim surrounding the 5.25" drive assembly bezels could then be removed. This allowed the assembly to be pushed back into the drive bay where it could be lifted out from the rear. The assembly could then be extracted, albeit narrowly missing the power supply. As I surmised, it's one of those things that are straightforward once the technique has been revealed!

The next thing I tried was to add another 5.25" drive. The first problem encountered was that the rear of the lower drive came into contact with the power supply. After removing the power supply I found that the front bezel of a standard 5.25" is wider than the IBM ones, so it wouldn't fit through the drive bay aperture.

I followed this by removing the new 5.25" drive and replacing it with a 3.5" one, using a 5.25 to 3.5" adapter tray. This almost worked. As before, the bezel of the adapter tray was too wide. A bit of judicious filing sorted that out. The next problem was that the drive bay itself was such a tight fit on the drive that the heads of the screws attaching the adapter tray to the side plates of the drive assembly protruded enough to prevent the assembly fitting comfortably in the drive bay.

This is as far as I've got this evening, but at least I'm now in a position to get it sorted out, assuming the drive controller can handle the 3.5" drive.

One interesting item I came across while browsing Jim's site was the mention that on one of his machines, an early IBM PC 5150 from 1982, the system boots with the hard drive as A: and the floppy drive as C:!

-- Iain

 

[Iain]

IBM XT-286 Mechanic Required...

I am pleased to report that I finally got my XT-286 back together again. It was a little more of a struggle than I expected (and I think the guy who designed the drive bay assembly should be shot) but I'm pleased with the result. (See attached pic). I've now succeeded in fitting an 80287 co-processor and the 3.5" second floppy drive, which were the two upgrades I was keen to incorporate. Now I want to just get back to using it.

The 3.5" drive is a 1.44 MB unit, and the old controller card didn't seem to raise any complaint about operating the newer floppy format. I'm running MS-DOS 6.22; I think it's necessary to run MS-DOS V3.3 or later to be able to access a 1.44 MB floppy.

-- Iain

 

[Terry Yager]

She's just lovely...

--T