Nc100 keyboard issue: only return and left key works

Started by Baracus, 04:07, 09 March 24

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Baracus

So I am trying to find out the problem on this NC100, as the keyboard does not work, except for the return and left arrow keys.

I reset it removing the batteries and at the date-time screen, I can go to the next field with return, or go back with the left key but no other key seems to work. Once I am on the main screen it does not go anywhere because no key shortcut works.

I opened up the device and cleaned with alcohol the connectors, which seems OK, and the ribbon cable. I opened the keyboard too and it seems fine. I see no signs of damage anywhere; there was just a bit of rust here and there around the battery spring and power connector, which I cleaned the best I could.

As I have a NTS Dreamwriter, I removed the keyboard from there, which works for sure, and placed it in the NC100 and it is doing the same problem, so the issue seems to be on the board, not on the keyboard itself. How can I find out what is the issue? Not even sure where to start as I don't see straight traces to an IC, so it is quite hard to find out even what to test for. :(

robcfg

I made this "x-ray" image from our pictures https://www.cpcwiki.eu/index.php/NC_Series_Mainboard_Versions 

You can see that the traces coming from the keyboard connectors go to the resistors on top of then and from there to the asic (the big square chip).

So, I'd check continuity across the resistors and from there to the asic, and check if the keyboard connectors have cracked solders.

If everything is fine and the asic has no corroded pins, then probably your asic is damaged.

Good luck!

Baracus

Thanks; will go for the full investigation then. BTW should I retouch the solder joints at all? My concern is that potentially going to re-heat a joint may break things, unless I re-do the whole solder joint from scratch.

If the ASIC is bad, I need a new board, right?

robcfg

I'm afraid that if the asic is damaged then, yes, you'll need a new board.

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