Need Help - Model M electrical problem

[fohat]

I have a very old Model M that Cindy has asked me to repair. It is a beautiful old industrial 1388032 ("Johnson Controls" branded with a big heavy shiny metal badge) from 1985 with bar code label and "mandolin crystal". It has been thoroughly cleaned, including De-Oxit on the electrical connections, and screw-repaired where a handful of rivets were missing.

Here is the problem: when connected with the SDL-PS/2 cable to my outboard Soarer's/Teensy converter box, it works properly with no problems or hesitation. But when I plug it (same cable, and I also tried another cable) into the PS/2 port on the motherboard, as soon as the power button is pressed all 3 LEDs start flickering wildly, and continue flickering through POST and boot-up. Keystrokes do not register at all under this condition.

Is it possible that the PS/2 port is not furnishing sufficient power for the keyboard? Do the very early Model Ms take more juice than the later ones? Would the USB connection through the Teensy be providing more?

I have never encountered anything quite like this before.

[XMIT]

I know that board. I hauled it out of the recycler's bin myself. It's an old Industrial M. I've got one here with a serial number within a couple hundred of that one. The "Johnson Controls" badge on that and the Industrial F is misleading. These are IBM boards, just like XMIT004.

XMIT004 front.

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XMIT004 rear.

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From my experience with these boards, the issue you've got is that the board outputs an odd variant of the PS/2 protocol that worked well with the Industrial PCs that accompanied these keyboards originally. Soarer's Converter will do the right thing, but many other converters won't. I'm willing to bet that the "PS/2 port on your motherboard" is really an internal PS/2-USB converter.

It could also be a power issue.

The most robust, and least authentic, fix is to replace the controller. Otherwise, simply use Soarer's Converter, that's what I do with mine.

[fohat]

Thank you for that. I was wondering if I was doing something wrong or missing something.

Anyway, guys, the keyboard is exactly like his, just 25 units down the production line at # 05278, with a handsome "Johnson Controls" badge that is bigger, thicker, and shinier than the IBM standard one. There could even be an IBM badge underneath it, for all I know, but I don't want to mess with it.

If someone is interested in it, let Cindy know because it will be easier for everyone to keep it all original.

[fohat]

Here are a couple of photos in case any of you guys are interested in this specimen.

Cindy will replace the missing caps, I'm sure.

[ekeppel]

I realize that this is a very old thread, but since it may help others in the future, I'll relate that I had the same experience with my 8032. It also had the flickering leds and nonresponsive keys.

What worked for me was to just swap the main controller chip from a similar vintage Model M controller. That allowed me to keep everything else original on the keyboard except for that one chip.

Of course you will want to use a proper desoldering setup and ESD protected workspace, but it's not a difficult job.