IBM PC 5150 keyboard connector repair

[mbbrutman]

I have two Model F keyboards (original PC or XT) that have gone bad due to an intermittent connection in the DIN connector.  I'm not sure how these were originally assembled, but in the mode of failure that I have the pins (embedded in the round black plastic that spaces them) come out of the rubber sleeve.  Pressing tightly restores connection for a little bit, but it is not really usable that way.

Since it was bad I finished the job and separated the pins to show you what I mean:



Finding the DIN plug is not a problem.  But I really don't want to hack off the end of the cable with the nice molded IBM plug.  These are not museum pieces, but I'd like the repair to be unobtrusive.

Has anybody else run into this problem and attempted a fix?  I'm also open to just replacing the cord entirely, but I doubt that there is a surplus of originals laying around anywhere.


[And my belated introduction ..  I am not much of a keyboard guy - just Model Ms and Model Fs.  I grew up on the PCjr Chiclet and 2nd revision keyboards so life was tough.  My only real keyboard claim to fame was managing to find the documentation on the IBM LPFK (Lighted Program Function Keys), which is more of a collection of buttons than a keyboard.]

Thanks in advance,

Mike

[tp4tissue]

 

You MONSTER!!!!

Poor keyboard. 

[Soarer]

Obviously it needs resoldering somehow, and then glue it, I guess!

Can the cable be pushed through or is it bonded?

What does it look like inside the casing?

[mbbrutman]

You MONSTER!!!!

Poor keyboard. 

I think you misunderstand.  The connections were already intermittent and broken.  Without examining it there is no way to fix it.  I'm trying to fix it properly, saving the rubber molding instead of just hacking a new end on.

[mbbrutman]

Obviously it needs resoldering somehow, and then glue it, I guess!

Can the cable be pushed through or is it bonded?

What does it look like inside the casing?

The exposed ends of the pins that you see there disappear into more black plastic or potting compound.  I presume that they are soldered back in there, where I can't see them.  That is also where the connection has gone bad.

I suspect when the cable was assembled it was pushed through.  But it is possible that a chemical or heat was used at the time it was assembled, and I have no chance in h-ll of pushing it through again.  Unless somebody knows a good trick, cutting the molded connector seems to be the only way in.

(I might try a heat gun to see if I can loosen it up, but I'm also scared to damage the rubber/plastic beyond repair.)

[Soarer]

Hmm, I see. Looking at one of mine, it appears that the cable is free to move inside the strain relief part of the housing, so perhaps your best option is to try and dig (or drill?) the potting compund or whatever out. I'd avoid heat

[rootwyrm]

It's not actually soldered in there, most likely. It's epoxied around the pin housing. The epoxy appears to have failed. (I don't see any evidence of solder, that's why I think it's a push-in.) The possibility is that the interior wire connections are faulted.

[mbbrutman]

This is what it looks like disassembled:



I used a little heat from a hair dryer to soften it up a bit, and then a little twisting on the wire and the molded plug.  I was hoping the wire and the assembly would spin free, but the wire broke off instead.  But that allowed me to push the middle part completely out.

I think at this point I can get a few generic DIN plugs to experiment with.  After the connections are made I can slide the molded rubber plug back and it should be a very good repair.

[mbbrutman]

Ok, it's repaired ...  here is a picture of the new innards with the original cable and plug housing.



An expert at the antiques roadshow might figure out that the cable is 1.25 inches shorter than it should be, and that the connector is not original.  But the XT is pretty happy with it. ; - 0


Mike

[mbbrutman]

One last post - a link to a more detailed writeup on how to do the repair:

http://www.brutman.com/IBM_PC_Keyboard_Plug_Repair/IBM_PC_Keyboard_Plug_Repair.html


Mike

[Soarer]

That's a good-looking fix, and a very thorough write-up - thanks!

[mbbrutman]

Thanks,

I figure that if I can keep somebody else from junking a classic like this, then it was worth the effort.  The $5 keyboard that came with my recent Dell workstation won't be so lucky. ; - 0


Mike