Adapting P70 Keyboard to PS/2

consideringquiet

18 May 2019, 22:04

Hello.

Recently I came across a P70 keyboard which I hoped to easily convert to PS/2. However, it turns out to not be as easy as is reported by every single post on here.

I spliced up a Fellowes Keypad, which had wires of orange, red, brown, and black color. My friend tested for continuity, and two led to pins reported as "n/c" or not connected. We assumed that the pins were for split PS/2, and coded the orange as data and the brown as clock.

Orange matched up to pin 2 on the ps/2 pinout. Brown matched up to pin 6.

We used jumpers to match as follows:

Fellowes Keypad - P70
Orange ("Data") - Red
Brown ("Clock") - Green
Red ("VCC") - Yellow
Black *"GND") - Black

However nothing happened when we plugged it in. No light or any response from the keyboard whatsoever.

Any help would be appreciated.

Here is the photo I used to attempt the first wiring:
8573_KB_conn2..gif
8573_KB_conn2..gif (4.07 KiB) Viewed 604 times
150px-MiniDIN-6_Connector_Pinout.svg.png
150px-MiniDIN-6_Connector_Pinout.svg.png (21.01 KiB) Viewed 592 times
Last edited by consideringquiet on 18 May 2019, 22:23, edited 2 times in total.

User avatar
snacksthecat
✶✶✶✶

18 May 2019, 22:12

The first thing to check would be is it getting (enough) power?

Do you have a multimeter?

Open up the keyboard and look for all of the ICs (chips).

Use your multimeter to measure the voltage by touching the probes to the pins indicated in the picture.

Image

Each one should measure close to 5v (probably like 4.6-4.8 in reality).

Note: these aren't always the Vcc and Gnd pins, just very frequently. If you google the number written on each chip, you can usually find the datasheet which will tell you the exact pinout of the chip.

consideringquiet

18 May 2019, 22:18

snacksthecat wrote:
18 May 2019, 22:12
The first thing to check would be is it getting (enough) power?

Do you have a multimeter?

Open up the keyboard and look for all of the ICs (chips).

Use your multimeter to measure the voltage by touching the probes to the pins indicated in the picture.

Image

Each one should measure close to 5v (probably like 4.6-4.8 in reality).

Note: these aren't always the Vcc and Gnd pins, just very frequently. If you google the number written on each chip, you can usually find the datasheet which will tell you the exact pinout of the chip.
I'm not certain it's possible for me to disassemble it, just due to the sheer number of clips the keyboard uses to stay together. I do not wish to damage the board further than I already have.

Is there any other way I can attempt to solve this externally? I fear I may have permanently damaged the board through attempting to test it.

consideringquiet

18 May 2019, 22:20

Also, I saw a comment online instructing not to join the two shield grounds. Is there any reasoning for this?

User avatar
snacksthecat
✶✶✶✶

18 May 2019, 22:21

Can you post the ps2 pinout picture you referred to in the OP?

consideringquiet

18 May 2019, 22:23

snacksthecat wrote:
18 May 2019, 22:21
Can you post the ps2 pinout picture you referred to in the OP?
Sure:
150px-MiniDIN-6_Connector_Pinout.svg.png
150px-MiniDIN-6_Connector_Pinout.svg.png (21.01 KiB) Viewed 595 times

User avatar
snacksthecat
✶✶✶✶

18 May 2019, 22:29

You confirmed with the continuity tester that each of the colors from the keypad cord correspond with those positions in your ps2 pinout image?

I'll keep thinking but nothing is jumping out at me immediately. Do you have a teensy? Soarer's simple logic analyzer would be a good tool to test with if you do have a teensy or promicro board laying around.

consideringquiet

18 May 2019, 22:33

snacksthecat wrote:
18 May 2019, 22:29
You confirmed with the continuity tester that each of the colors from the keypad cord correspond with those positions in your ps2 pinout image?

I'll keep thinking but nothing is jumping out at me immediately. Do you have a teensy? Soarer's simple logic analyzer would be a good tool to test with if you do have a teensy or promicro board laying around.
I did, however, two cables led to pins that are supposedly not supposed to be connected as per the image.

I do have a teensy, but its not really usable right now. Still sitting in my failed NCR 4950 project. I can't seem to catch a break here.

Delirious

19 May 2019, 00:35

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consideringquiet

23 May 2019, 02:44

Delirious wrote:
19 May 2019, 00:35
3F6F53CB-5B09-4DE8-BC3D-03F53FF105D9.jpeg

EBD0B4CC-5D82-4CD2-A447-8C63DFAC682E.jpeg

E98F7EC3-F55B-4DBF-89CC-BBE3F9792A32.jpeg

99C817E0-E1AE-4EF0-9D17-9C149C0E6141.jpeg
I'm sorry, Is there any way of doing the conversion without opening the case?

consideringquiet

24 May 2019, 02:21

Has anyone done this conversion before?

User avatar
Chyros

27 May 2019, 09:07

I literally just connected the wires from the PS/2 cable to those from the P70's; twisted them together and then joined by soldering. I can't remember the details anymore unfortunately; it's been a while. If you want I can unscrew my converter box and look inside at what I did :) .

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