Nord electro 6d - broken diodes in keys pcb

[spunko]

Hello, I'm new to the forum. My Electro 6d has one key that is not working, it only works in organ. Almost everytime this is just cleaning, but when I open it I noticed that 2 diodes from that key were broken. What would be the correct replacement for those diodes?
Thank you very much.

[spunko]

They look like standard 1n4148 (it should be written on the diode side, check a non broken one), if you look at how a keyboard matrix is arranged in fact they are just there to keep the right polarity during the scan, which is done at low voltage so no need for any special requirement.

Real question is: how/why did those diodes break in that way? I suggest you check all of them, also the ones which don't look broken.

https://doepfer.de/DIY/Matrix_61.gif

[spunko]

Thank you very much. They are indeed 1n4148. I have those diodes in my toobox so I changed those 2 broken diodes, tested and then also the key next to the left won't sound at all, not even in organ. The inital faulty key keeps sounding in organ, but not in other modes like from the start.

Took everything apart again, checked the PCB and found a third diode broken in half, why did it broke? it was good just minutes ago when tested all diodes. Anyways, replaced that one diode too and now I'm back at the start, the initial faulty key only sound in organ, not in other mode. The second faulty key is now working good. No other key is faulty.

Also checked continuity from the carbon pads to the ribbon cable socket, all good. If the diodes are ok now, Why the key still doesn't sound?

Sorry for the bad english.

[spunko]

I suggest you check also all circuit tracks for continuity, based on the schematics I attached above (diodes don't break casually, there may be some shortcircuit or open connection) , then also the ribbon cables and finally the connectors (unplug, clean, replug carefully)

PS: if that key is still not sounding then the contacts on rubber side may be dirty or worn (and in that second case you need to replace the whole strip).