Author Topic: [Help] IBM Model M Indicator Lights not working  (Read 466 times)

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Offline PRoman

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[Help] IBM Model M Indicator Lights not working
« on: Mon, 17 May 2021, 04:05:22 »
Hi, i have a problem with my Lexmark 1993 Model M, the keyboard works on my 2 PCs with direct ps/2 without using adapter. but the the indicator LEDs do not light. I tested with other indicator led board, and i disconnected the leds ribbon cable and i tested it conductivity with a multimeter, it works. I think it may be something related to the PS/2 port. Does anyone know how to fix it? English is not my native language, I hope it is understood
« Last Edit: Mon, 17 May 2021, 04:16:05 by PRoman »

Offline yui

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #1 on: Mon, 17 May 2021, 04:26:04 »
So 1st, does the board work? as does it output characters when you type on it?
 -If yes, then the problem is either likely software side (windows drivers/config, OSX/linux firmware/config) or that there is something wrong with the connections in the board, tbh my lexmark M is the terminal kind and does not have LEDs so i am out of my depths here, or it could be that the controller is damaged, but that is rather unlikely.
 -If partially (the keyboard works sometimes randomly stops, outputs long strings of the last char you pressed), then i would expect that either your usb port is not supplying enough current (if you are on a hub for example) or that your converter is not M compatible and crashes (had that with a belkin ps2 to usb, a dock with integrated converter and a random no brand in wire converter). 1st step if you are on a hub is to plug on the pc directly, 2nd is to change the converter.
 -If no, then the controller is not initializing, and that could come from a lot of things, from a dead board, dead converter, windows 8 having ps/2 capabilities disabled by default, pc/macs with incomplete USB compliance cutting power.

a lot of this comes from power, the M is a rather power hungry board, especially the old ones, so it can be rather hard to drive.
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Offline PRoman

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #2 on: Mon, 17 May 2021, 04:39:26 »
So 1st, does the board work? as does it output characters when you type on it?
 -If yes, then the problem is either likely software side (windows drivers/config, OSX/linux firmware/config) or that there is something wrong with the connections in the board, tbh my lexmark M is the terminal kind and does not have LEDs so i am out of my depths here, or it could be that the controller is damaged, but that is rather unlikely.
 -If partially (the keyboard works sometimes randomly stops, outputs long strings of the last char you pressed), then i would expect that either your usb port is not supplying enough current (if you are on a hub for example) or that your converter is not M compatible and crashes (had that with a belkin ps2 to usb, a dock with integrated converter and a random no brand in wire converter). 1st step if you are on a hub is to plug on the pc directly, 2nd is to change the converter.
 -If no, then the controller is not initializing, and that could come from a lot of things, from a dead board, dead converter, windows 8 having ps/2 capabilities disabled by default, pc/macs with incomplete USB compliance cutting power.

a lot of this comes from power, the M is a rather power hungry board, especially the old ones, so it can be rather hard to drive.

The keyboard works perfectly (all keys work, caps lock and num lock do their job), not keys delay, not repeated chars, not stops, except for the leds, they never turn on. I'm using the keyboard directly to ps/2 port of the motherboard with the original SDL to ps/2 cable. I think is software or electrical supply issue.





Offline PRoman

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #3 on: Mon, 17 May 2021, 04:45:32 »
So 1st, does the board work? as does it output characters when you type on it?
 -If yes, then the problem is either likely software side (windows drivers/config, OSX/linux firmware/config) or that there is something wrong with the connections in the board, tbh my lexmark M is the terminal kind and does not have LEDs so i am out of my depths here, or it could be that the controller is damaged, but that is rather unlikely.
 -If partially (the keyboard works sometimes randomly stops, outputs long strings of the last char you pressed), then i would expect that either your usb port is not supplying enough current (if you are on a hub for example) or that your converter is not M compatible and crashes (had that with a belkin ps2 to usb, a dock with integrated converter and a random no brand in wire converter). 1st step if you are on a hub is to plug on the pc directly, 2nd is to change the converter.
 -If no, then the controller is not initializing, and that could come from a lot of things, from a dead board, dead converter, windows 8 having ps/2 capabilities disabled by default, pc/macs with incomplete USB compliance cutting power.

a lot of this comes from power, the M is a rather power hungry board, especially the old ones, so it can be rather hard to drive.

The keyboard works perfectly (all keys work, caps lock and num lock do their job), not keys delay, not repeated chars, not stops, except for the leds, they never turn on. I'm using the keyboard directly to ps/2 port of the motherboard with the original SDL to ps/2 cable. I think is software or electrical supply issue.
.

Now that I remember, the first week when I assembled the keyboard and used it, the LEDs were blinking a few times randomly (when caps lock was on, or num lock). after about a month, they never turned on again
« Last Edit: Mon, 17 May 2021, 04:48:59 by PRoman »

Offline yui

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #4 on: Mon, 17 May 2021, 04:50:37 »
The keyboard works perfectly (all keys work, caps lock and num lock do their job), not keys delay, not repeated chars, not stops, except for the leds, they never turn on. I'm using the keyboard directly to ps/2 port of the motherboard with the original SDL to ps/2 cable. I think is software or electrical supply issue.
if it works properly it is not supply, a supply problem would prevent the board from even working at all, or would make it output very strange things. as you said that works, supply is out of the picture, and being on the ps/2 of the motherboard should also insure that.
to see if it is windows f***ing up or a problem with the board when the board initializes it blinks its LEDs, if they blink when you start the PC, the problem is software side, if it doesn't the problem is board side (this blinking is 100% board side), one other thing you could try is to enable numlock on boot, although windows 10 will disable it and you can't prevent it from doing so (thx MS), if the light is up until windows boots then that also mean the problem is software side. although further than that i will be unable to help as it would be the 1st time i see that problem.
vi vi vi - the roman number of the beast (Plan9 fortune)

Offline PRoman

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #5 on: Mon, 17 May 2021, 04:57:20 »
The keyboard works perfectly (all keys work, caps lock and num lock do their job), not keys delay, not repeated chars, not stops, except for the leds, they never turn on. I'm using the keyboard directly to ps/2 port of the motherboard with the original SDL to ps/2 cable. I think is software or electrical supply issue.
if it works properly it is not supply, a supply problem would prevent the board from even working at all, or would make it output very strange things. as you said that works, supply is out of the picture, and being on the ps/2 of the motherboard should also insure that.
to see if it is windows f***ing up or a problem with the board when the board initializes it blinks its LEDs, if they blink when you start the PC, the problem is software side, if it doesn't the problem is board side (this blinking is 100% board side), one other thing you could try is to enable numlock on boot, although windows 10 will disable it and you can't prevent it from doing so (thx MS), if the light is up until windows boots then that also mean the problem is software side. although further than that i will be unable to help as it would be the 1st time i see that problem.

Leds not blinking on start pc, not in BIOS, and not in POST. The data signal is losed somewhere on the plate. I will be trying some things, if I find the solution I will post it.


Offline yui

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #6 on: Mon, 17 May 2021, 04:59:49 »
Now that I remember, the first week when I assembled the keyboard and used it, the LEDs were blinking a few times randomly (when caps lock was on, or num lock). after about a month, they never turned on again
the electronic tinkerer in me thinks that this is corrosion in a connector, maybe try to brush (soft metal brush) the connector where the ribbon cable plugs in (i would not recommend chemical deoxidizers unless someone else has tried them as the coating on those ribbons are rather weak to chemicals). or maybe the common trace got corroded.
The carbon coating on the ribbon contact should be black, it is normal and do not remove the black from there! (some have done so in the past, and regretted it)
if you can't brush the connector, then reinserting the ribbon a few time could work, but those are rather fragile.
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Offline PRoman

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #7 on: Mon, 17 May 2021, 16:35:41 »
Now that I remember, the first week when I assembled the keyboard and used it, the LEDs were blinking a few times randomly (when caps lock was on, or num lock). after about a month, they never turned on again
the electronic tinkerer in me thinks that this is corrosion in a connector, maybe try to brush (soft metal brush) the connector where the ribbon cable plugs in (i would not recommend chemical deoxidizers unless someone else has tried them as the coating on those ribbons are rather weak to chemicals). or maybe the common trace got corroded.
The carbon coating on the ribbon contact should be black, it is normal and do not remove the black from there! (some have done so in the past, and regretted it)
if you can't brush the connector, then reinserting the ribbon a few time could work, but those are rather fragile.

Today i tried the following:

-Brush the connector; not working
-Changing the electronics board and leds board for other that have the LEDs ribbon cable integrated into membrane cable adapting it. I got a keyboard working properly, all keys work, no delay, etc, but leds never blinking.

I dont think the problem is the sdl cable because the keyboard is working properly. I don't think either is the membranes, caps lock is working.
I tried other PC, i tried on Linux or Windows, not working. Basically i changed almost every part of the keyboard except membranes, cable and keys.

The only thing that occurs to me is that I have two led boards that are dead, I will be testing that boards, and i'll try the keyboard in a more old PC.


Offline yui

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #8 on: Tue, 18 May 2021, 01:27:25 »
either the LED boards are dead or the common trace in the ribbon or on controller card is corroded, or your controller is defective and its LED output has fried for some reason, or maybe it has fuses on the board and those are blown, as i said my only old M does not have LEDs and the unicomps are built very differently, so i can only give help with theories, i wish someone like fohat could see this thread, he is a wizard when it comes to M
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Offline Snowdog993

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #9 on: Tue, 18 May 2021, 22:19:20 »
Do they flash when you first connect the keyboard?
If they do, then power is getting to the controller and LED's.
Undercurrent is usually an issue if you are not using PS/2. The power for the PS/2 port is about 6-10x the average USB port. A good fix is finding a good USB to PS/2 adapter. Try a different USB port as well. If you use the ones on the front panel, you may want to go around back and try the ones in the back.
If you are using it on a PS/2 port, maybe you need the 4-pin lead to the LED's replaced. Hmm.
The other part connects to the controller pins 9-12.
Hope this helps.
« Last Edit: Tue, 18 May 2021, 22:22:06 by Snowdog993 »

Offline Snowdog993

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #10 on: Tue, 18 May 2021, 22:32:32 »
Today i tried the following:

-Brush the connector; not working
-Changing the electronics board and leds board for other that have the LEDs ribbon cable integrated into membrane cable adapting it. I got a keyboard working properly, all keys work, no delay, etc, but leds never blinking.

I dont think the problem is the sdl cable because the keyboard is working properly. I don't think either is the membranes, caps lock is working.
I tried other PC, i tried on Linux or Windows, not working. Basically i changed almost every part of the keyboard except membranes, cable and keys.

The only thing that occurs to me is that I have two led boards that are dead, I will be testing that boards, and i'll try the keyboard in a more old PC.

After reading this, the culprit is not the keyboard at all. It is your USB to PS/2 adapter.

Offline yui

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #11 on: Wed, 19 May 2021, 02:43:43 »
After reading this, the culprit is not the keyboard at all. It is your USB to PS/2 adapter.
pls read the whole thread... there is no usb to ps/2 controller in his setup. so no it is not the problem, also the light went out progresively but started out working, and the everything else on the board is working, so pretty much a guaranty that the communication between the PC and board is fine, and so likely is the controller.
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Offline Snowdog993

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Re: [Help] IBM Model M Indicator Lights not working
« Reply #12 on: Wed, 19 May 2021, 20:08:56 »
After reading this, the culprit is not the keyboard at all. It is your USB to PS/2 adapter.
pls read the whole thread... there is no usb to ps/2 controller in his setup. so no it is not the problem, also the light went out progresively but started out working, and the everything else on the board is working, so pretty much a guaranty that the communication between the PC and board is fine, and so likely is the controller.
Then do what I did with mine. Simple.
I sincerely doubt your controller "burned out" if it is working perfectly.
....and did you read what I said as well? It takes two to communicate.
4-pin arduino male to male connectors about 12" long should do the trick.
« Last Edit: Thu, 20 May 2021, 10:25:45 by Snowdog993 »