Faulty STe Keyboard

[logronoide]

Hello everyone,

I recently acquired a French version Atari 520STe with a 1.62TOS and its keyboard, but unfortunately, the keyboard is malfunctioning. To isolate the problem, I tested it with a UK keyboard from another STe, and everything worked smoothly, confirming that the issue is not with the motherboard.

The keyboard isn't entirely non-functional; the mouse, joystick, and 70% of the keys still work. I've cleaned the contacts and inspected them for any visible damage but couldn't find any broken tracks. Interestingly, the non-working keys seem to follow a pattern, mostly located on the left side of the keyboard:

F1 to F7
ESC to 3
TAB to E
CTRL to D
LEFT SHIFT to X
Additionally, these standalone keys are also not working: Alternate, 0, -, Backspace, Right Shift, Up Key, Numeric Keypad ) and Numeric Keypad *.

I suspect the problem might be with the C070122-002 chip. In the other STe, this chip is soldered, whereas in this one, it's socketed. So I can't test this. However, I'm not entirely sure, so I'm seeking advice here.

Could you suggest what steps I should take to confirm if the C070122-002 chip is indeed the issue? Any insights or recommendations would be greatly appreciated.

Thanks a lot!
Best regards,
Diego

[rubber_jonnie]

Honestly I'd start by stripping it down and closely inspecting the PCB for cracks, the cable for failures (I had one wire fail on mine with similar results) and checking for contaminants causing the contacts to fail.

[logronoide]

Thank you! You were right. It took me 5 minutes to realize where the problem was. I guess they are broken tracks due to an impact. Some pictures:

broken-keyboard-board-medium.jpeg (234.55 KiB) Viewed 1693 times

broken-keyboard-board-detail.jpeg (270.4 KiB) Viewed 1693 times

I think I can manually re-wire those tracks with thin wires, but if anyone has suggestions to fix the tracks on the board, I'm happy to listen!

[stephen_usher]

This schematic may help.

Atari_ST_USA_Keyboard_Schematic.jpg (182.28 KiB) Viewed 1736 times

[logronoide]

This schematic may help.

Atari_ST_USA_Keyboard_Schematic.jpg

Thank you! Yes, I was looking for an schematic and this one is perfect!

[DoG]

Classic. Someone raged during gameplay and hit the keyboard in the center. There is a stem holding up the keyboard in the middle that breaks the pcb when hitting it to hard. I have done some repair and Steve did great job with his.

[rubber_jonnie]

Thank you! You were right. It took me 5 minutes to realize where the problem was. I guess they are broken tracks due to an impact. Some pictures:





I think I can manually re-wire those tracks with thin wires, but if anyone has suggestions to fix the tracks on the board, I'm happy to listen!

Hi, your images aren't working for me as they are linked to an outside website. Can you edit please and upload them to the forum then place them inline please.

Cheers, RJ

Otherwise, glad you found the issue, something fine like 30swg kynar wire should do the trick. Just be sure to put conformal coating or solder mask (or whatever you use) over any bare parts of the wire before reassembling.

[rubber_jonnie]

Thank you! You were right. It took me 5 minutes to realize where the problem was. I guess they are broken tracks due to an impact. Some pictures:

broken-keyboard-board-medium.jpeg

broken-keyboard-board-detail.jpeg

I think I can manually re-wire those tracks with thin wires, but if anyone has suggestions to fix the tracks on the board, I'm happy to listen!

Yep, rage quitting has a long and varied history...

[logronoide]

Great news - I managed to fix the keyboard!

First, I carefully scratched the traces to expose the copper lines. This allowed me to repair all the original traces successfully. However, during the process of cleaning the board with isopropyl alcohol, one of the traces at the top started to disintegrate. It seems the board's age made it quite fragile.

To address this, I had to rewire the damaged track using a yellow cable. And this time, I decided not to clean the board to avoid further damage.

Here's a photo showing the scratched traces:

broken-keyboard-scratched-traces.jpg (145.43 KiB) Viewed 1685 times

And here's how it looked after the rewiring:

broken-keyboard-traces-patched.jpg (198.74 KiB) Viewed 1685 times

On a lighter note, I initially thought the numbers below the function keys weren't working. Then it hit me - I was using a French keyboard, which requires holding the shift key to type numbers! A bit of a facepalm moment there.

Thanks a lot for all your help and suggestions!

Cheers,
Diego