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PS/2 Keyboard Wiring Repair

7,955 961 June 1, 2012 at 07:59 AM
I found a mechanical keyboard with the PS/2 wire cut. There are 5 wires and I need to know the correct wiring.

Some pics of the controller board:

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#2
I would cut the plug and wires off of another PS/2 Keyboard and try to solder them together.
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#3
Quote from beefcake78
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I would cut the plug and wires off of another PS/2 Keyboard and try to solder them together.
Yeah that's what I am trying to do but I am unsure of the wires. Red is probably 5V and black is GND, the other black is some sort of shielding or something, not sure of the other 2 colors.
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#4
Well, I don't think you can hurt much if you guess and get it wrong. Imagine how many keyboard cables get shorted out by pets or kids chewing on them?
http://en.wikipedia.org/wiki/PS/2_connector
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Quote from beefcake78
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Well, I don't think you can hurt much if you guess and get it wrong. Imagine how many keyboard cables get shorted out by pets or kids chewing on them?
http://en.wikipedia.org/wiki/PS/2_connector
Yeah I'll just try it out and see if it works and switch wires if they don't, figure I ask here just in case.

Thanks for the help.
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Ok I'll ask..why would you bother, unless its just a hobby, I mean they are so cheap to find or use a USB to PS/2 adapter.
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#7
Don't make any assumptions about the wire colors and their functions because NMB not only doesn't use the normal red for +5V and black or GND, but their colors aren't even consistent among models. So I think you should trace out the circuit board from the leads of that capacitor (16 volts, 10uF) in the upper left corner to see where the +5V and GND are and then guess about the data and clock wires because it seems that getting clock and data reversed doesn't cause any damage.

Here's some examples of how NMB wiring is wierd:

NMB model RT101+:


cable connector pinout, from top to bottom:
  • chassis ground (black)
  • +5V/+12V (brown) Original Compaq computers used +12V for their keyboards
  • ground (red)
  • keyboard reset (green)
  • data (white)
  • clock (black)


NMB model RT6255+:


cable connector pinout:
  • unused (empty, but goes to chassis ground)
  • +5V (brown)
  • signal ground (white)
  • data (red)
  • clock (green)

The signal ground and chassis/cable-shield ground may be completely separate, and in that RT6255+ keyboard the cable-shield ground lug doesn't go to anything inside, maybe because of ground loop problems. BTW, NMB keyboards can have identical model numbers but be completely different inside because the RT101+ above uses membrane switches, but I have another RT101+ with metal mechanical switches.
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Quote from repitall
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Ok I'll ask..why would you bother, unless its just a hobby, I mean they are so cheap to find or use a USB to PS/2 adapter.
It's not just a hobby; it's a lifestyle, dammit!

Keyboards with mechanical switches cost at least $60, and a lot of those USB to PS/2 adapters don't work very well if you type fast or have to hold down more than one key at a time (gaming): GeekHack.com review of adapters [geekhack.org]
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#9
Thanks for the info larry.
Quote from repitall
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Ok I'll ask..why would you bother, unless its just a hobby, I mean they are so cheap to find or use a USB to PS/2 adapter.
You never want to use a mushy $5 keyboard once you use mechanical keyboard. A new one can cost $100 or more. Besides that, if feels good to make broken things work and it gives me something to do. I think I am going to dye the keyboard too. laugh out loud
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Last edited by ikonoklast June 2, 2012 at 09:46 AM.
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#10
pinouts.ru/Inputs/KeyboardPC6_pinout.shtml

I would normally suggest that but of course colors aren't common.

the types of components that the leads are connected to should give you clues as to what they are for; e.g. ground vs power vs clock, etc. I'm not an electrical engineer so I can't really help there.
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#11
Quote from ikonoklast
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Thanks for the info larry.

You never want to use a mushy $5 keyboard once you use mechanical keyboard. A new one can cost $100 or more. Besides that, if feels good to make broken things work and it gives me something to do. I think I am going to dye the keyboard too. laugh out loud
You're dedication is making me want to pull out the Focus 2001 tactile feel keyboard from my box of 1990's PC parts... Slowly purging the Seagat MFM hard drives out of this same box laugh out loud
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Quote from beefcake78
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Focus 2001 tactile feel keyboard from my box of 1990's PC parts...
Is that the one with the turbo button in the middle of the cursor keys?

BTW Monoprice has PS/2 adapter cables for those AT keyboards for 72¢ + about $3 shipping. I ordered 30 of them for some IBM keyboards, and all 30 worked fine. The cheapest eBay source wanted $1.50 apiece, delivered.
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