Apple Extended Keyboard repair help

[3lectr1c]

I’ve got an original AEK with a bad left shift key. I took the assembly apart and noticed some corrosion in one area and I cleaned it up. Two traces are bad and I traced one of them back to said left shift key, great! The other leads to an option key.

So I traced the trace all the way to a pin on one of the ICs and soldered a bodge wire. Now the shift key acts stuck down at all times. Any ideas?

 

[davidg5678]

You can try desoldering the key switch and testing it in isolation. That way you'll know with certainty if it's the switch or the PCB at fault.

Sometimes, the diodes can go bad on the AEK, which disrupts part of the keyboard matrix. More than two keys would probably stop working if this is the fault you are experiencing. From what I recall, you can test the diodes without taking the keyboard apart any further, and if one is bad, you can bodge a replacement diode right onto the back of the PCB.

 

[3lectr1c]

I just tested in circuit and the switch does appear to be stuck shorted. Good point though that it may be the PCB at fault as well, I’ll desolder the switch when I have time and then I’ll have a look if it’s really bad or if it’s the board. I hope it’s the switch.

 

[3lectr1c]

Good news! The problem resolved itself. Who’s to say why, good thing is it works now! I’ve gone ahead and also soldered up the bodge for the left option key, and I finished cleaning it up. All reassembled now and working great! All for just $5 and a bit of time, definitely worth it!

 

[ShadeDream]

Sounds like something inside the switch is possibly problematic. Alps switches are not terribly dust or moisture proof and both can cause problems eventually inside the switch. You can (carefully) open alps switches without desoldering them if you wanted to examine the leaf and contacts for corrosion and/or to clean the switch out. Whatever issue was causing it to be stuck open might rear it's head again later, so might be useful when/if that occurs.

 

[3lectr1c]

I figured out what was causing it, the bodge I soldered was right next to a ground pin on the controller IC and it was bridging intermittently. All good now, not the switch at fault in the end

 

[ShadeDream]

Ops. That'll do it!