A1200 Ctrl key not working?

[oracle_jedi]

I have an A1200. Original Commodore model. North American spec.

 

The Ctrl key does not work, which among other things, means no hard reset short of power cycling the unit.

Every other key on the keyboard works ok.

 

I have reseated the ribbon cable with no luck.

 

I have tried to clean the keyboard connector on the motherboard with compressed air. No change.

 

I replaced the keyboard membrane with one of the new ones manufactured by RWAP. It made no difference.

 

I replaced the key spring mechanism with the Esc key. The Esc key works fine, the Ctrl key continues to do nothing.

 

Besides the Ctrl key, this Amiga seems to work fine. I don't think it has been recapped and I am hesitant to do so as I have little experience with SMT boards. Could this really be a capacitor issue?

 

Any suggestions on what to try next?

[Sinphaltimus]

Tray using a multimeter and test for continuity through the traces from the connector to the key make sure a solder point or something isn't bad.

[oracle_jedi]

Okay I have been doing some reading and researching.

 

And I have learned that the Ctrl key is Pin 11 on the ribbon connector.

 

http://www.amigahistory.plus.com/a1200info2.txt

 

And that connects to PD3 (pin 35) of the Keyboard MPU, which is U13 on the motherboard.

 

http://www.freeinfosociety.com/electronics/schematics/computer/pictures/amigaa1200keyboard.gif

 

I see a mark on the chip which I am assuming is Pin 1, but it is in the middle of chip, not on the edge.

 

Can someone confirm for me which is pin 35 on the Keyboard MPU?

 

Am I on the right track here?

Edited April 23, 2017 by oracle_jedi

[oracle_jedi]

Okay so I traced the circuit with a multi-meter and I can find no evidence of a break between pin 11 of the keyboard connector or pin 35 of the keyboard controller.

 

So my choices seem to be; either the keyboard controller chip is bad (on just one pin), or the keyboard connector itself is bad.

 

I think the more likely scenario is the white plastic keyboard connector.

 

Does anyone sell replacements? I googled but could not find any.