Lexmark M13 Cable Conversion

[SunshineRag_DT]

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Posting my next project. I currently have a Lexmark M13 (P/N:1403380) that I got a great deal on a few years ago. It is completely usable, but as with many of these the cables sheath is degraded and basically flaking off you can see the electrical tape trying to stem the inevitable tide. Also the connectors are suboptimal to say the least, being a DIN with a mouse serial connection.

Here is the current hideous connection and cables, boy does this look like a rats nest. On the keyboard side we have a DIN to PS/2 to USB active converter. On the mouse side I actually found a serial to USB adapter that works well as the only other option is a old KVM interface but any serial to USB convertors seem to be harder to find.

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So the cable itself is toast, the sheath is going to completely come off eventually, but even if it wasn't that connection stack is very hillbilly. Would like to get a cleaner connector stack and I have come up with a few options. Want to be able to revert back to be old cord to keep it stock. Also looking for some community input. Here are my current thoughts:

1.) If I could find a replacement cable I could just fix that, but does not appear Unicomp still have them. And does not really solve that mess of converters.

2.) Also it seems the sheath from the keyboard to the Y is what is failing, the Y to the DIN seems to be ok. I wonder if there could be a way just to resheath to the Y?

3.) Would love to find the PS/2 controller version of these old FSR boards, but due to rarity I suppose that is a pipe dream.

4.) I would really like to get a dual PS/2 out but a serial to PS/2 adapter seems not to exist in the current market, outside of old pricey KVMs. I have a dual PS/2 Y cable from Unicomp, and the DIN to PS/2 is simple, but would likely have to make a bit banging converter with a PIC to get the serial to PS/2. Here is the place to start with that, https://www.gedanken.org.uk/electronics ... s/ps2.html. Does not look overly hard but no idea if it will work and I have to invest in a PIC programmer actually get that all setup, will be alot of trial and error for me at least and I have to sort out PIC programming. There is a limit to how many new tricks you can teach this old dog.Probably the hardest path but would be exactly what I want.

5.) The easy path might be dual USB. I could use the current connector chain and get the converters to go into inside the keyboard and clip the unicomp Y connection PS/2 cable and rewire for USB out. This would be usable, but double USB just does not feel right and there would be alot of crap to cram in the case. Would have strip the enclosures off the current conversion components and see if I can jam them in and connect.

6.) Finally I could go single USB out, but that would also require stuffing a USB hub somewhere in addition to all the stuff above. I could then get just a single USB connector out very clean and tidy, assuming that the power requirement of all this still fit.

Wondering if anyone has any other thoughts or suggestions on this?

[Maledicted]

Maybe Unicomp's Endura Pro controllers are compatible? They offer them in ps/2 and USB, so that might literally be the only thing you have to change.

I stuffed the guts of a ps/2 to USB adapter, bluetooth adapter, some laptop battery cells and battery controller and some beefy toggle switches into a Scorpius 35 so I don't see why gutting a USB hub, serial adapter and ps/2 adapter to stuff inside wouldn't be pretty easy to manage with a roomy M case.

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[clickykeyboards]

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3.) Would love to find the PS/2 controller version of these old FSR boards, but due to rarity I suppose that is a pipe dream.

@SunshineRag.

Can you post a photo of the internals of your model M13 keyboard (1403380) and the internal cable connector.

I have a few dusty boxes of old Lexmark model M keyboards that I picked up in the 2010's and I might have the spare parts on hand for you from a similar IBM model M13 92G7461

https://www.clickykeyboards.com/product ... -10-21-95/

[SunshineRag_DT]

Sure will open it later today and post a couple pics. Thanks!

[SunshineRag_DT]

Here is a pic of the controller board. J6 is the mouse buttons disconnected, I think J5 is the pointer stick (top left in the pic). Interesting I see a connector there on the left side that is unused, could that be a breakout for the mouse, I see in the pics of the IBM there is a similar connection that goes to the mouse breakout daughterboard, which the Lexmark does not have.

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[clickykeyboards]

Ok, let me do some digging in some of the old dusty boxes that I got from Lexmark warehouse.

I think the two keyboard and one trackpoint flex cables are the same pinout arrangement.
(92G7461) IBM model M13 == (1403380) IBM model M13.

Not sure about the condition of the integrated cable with dual-head ps/2 keyboard and ps/2 mouse on it though. It might have the same typical "Lexmark cheap cable rot that is common for model M keyboards from mid-1990s).

Will post photos later when I move around some containers and can confirm with the item in-hand.

[SunshineRag_DT]

Very nice, my keyboard was actually built only a week after the one in the link you posted and I assume from the same factory.

I do have a Unicomp SDL Y cable to dual PS/2 that I could likely splice in if needed but would be interested in getting another original cable to keep it vintage. Looking at the cable connector it seems to be only 6 pins on the one you have but 9 pins on mine? I guess it could be that the mouse goes out the PS/2 port on yours, but it is odd that it also has a Y cable with both Keyboard and Mouse P/S2 but maybe the PS/2 requires less connections than serial mouse + PS/2 keyboard cable that I have. But if I replace the controller that will probably sort itself out, but I am not sure I could use the same cable only as the wiring will be different.

Also do you know if that controller you have is a Unicomp on a Stick or actual Trackpoint II. I guess that would be the only other question is if the controller technology could be different, but the from your pic they both have the same 5 trace connector to the controller. I assume mine is Unicomp on a Stick but not sure?

[clickykeyboards]

@ SunshineRag. I found the following parts in the keyboard box that originally came from Lexmark keyboard factory when they were at 740 W New Circle Rd, Lexington KY. (Before Unicomp moved across town in Lexington by the railroad tracks)

1996 IBM model M-13 with trackpoint (92G7461) from 01/22/96. (Keyboard has the original IBM trackpoint II technology, not Unicomp pointer-on-a-stick variation)

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Along with a brand new multi-page foldout Lexmark keyboard marketing brochure

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Good news is that Lexmark brochure has some interesting photos and ad copy and tech specs for mid 1990's keyboards.

Bad news is that the Lexmark keyboard cable is showing the typical cable rot/deterioration seen in many (but not all) mid-1990's model M keyboards. Also, it looks like the connector for the trackpoint cable in the 92G7461 model M13 is slightly different style than your 1403380 model M13.

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I put it up the website if you are interested in purchasing the internal controller and the cable for $20. Might be an experiment to try to desolder/swap/resolder the trackpoint connector to transplant between the two controllers.

https://www.clickykeyboards.com/product ... ard-mouse/

[SunshineRag_DT]

Done. In that pic on the controller is the trackpoint connection J5 and is the mouse button connections J4?
(NVM, I see that J4 is the trackpoint connection and is smaller but with more traces (7 vs 5), interestingly the membrane seems to be the same size as the membrane on mine before it get widened to go into the triomate. I suspect that the Trackpoint II connection and controller is very different from the Lexmark branded controller (IBM strain gauge vs Lexmark FSR pointing tech) and sadly will be incompatible unless I can get my hands on the trackpoint tech.)

I also just noticed that EnduraPros have a completely separate trackpoint control board that would be compatible to convert this to PS2 and leave the main logic board for the keyboard control but merge them in the cable forking the cable power. You wouldnt have an EnduraPro control board?

[clickykeyboards]

Glad to hear that the Lexmark spare parts are useful to you. They have been sitting for so long in a box, that I had forgotten (and was then surprised) what else was still in storage.

Your package will go out via USPS this morning. Controller + cable + daughter board + 2 support mounts.

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Strange about the IBM trackpoint II connector vs the FSR differences between the two model M13 models. I skipped the EnduraPros because of the bad trackpoint sensitivity and poor usability on modern systems.

Good luck with your model M13 (1403380) restoration and would love to hear if successful.

[SunshineRag_DT]

Thanks even though I suspect it won't work just ship it and I will investigate the differences and report back here, for Science!

Appreciate all the assistance!