Ensoniq SQ-80 blown F3 and F4 fuses after keyboard mis-pin

I just performed a simple repair on my SQ-80 which required removing the keyboard (replacing CEM3379). The chip replacement was successful, but unfortunately the first column of characters on the display was not visible. I assume at this point that I had just not reseated the keyboard cable correctly (as Sam mentions here that the communication path to the display goes through the keyboard).

Fine, so I open up the SQ-80 again and reseat the keyboard cable. I also visually confirmed at this point that none of the fuses were blown. But, unfortunately I was careless when reseating the keyboard cable, and I ended up not lining up the pins correctly - everything was shifted by one, such that the side with the red wire was disconnected. Of course I only realized this after powering up and seeing nothing but a faint glow on the display.

I discover my error when I open up the keyboard again, and I also see that fuses F3 and F4 are blown. Now (after correcting my error), I still see nothing when powering up. I’m hoping this is just because I haven’t replaced the fuses yet, and not because I’ve damaged the main board and/or display. I find it slightly reassuring that the service manual describes exactly what I’ve experienced:

If the ribbon cable is mis-pinned, fuses F3 and F4 will be blown.

So I suppose the next step is just to replace those fuses, but in the mean time, does anyone have experience with a problem like this?

I replaced the fuses and the synth is alive again! It still has the existing issue of two dead display characters, probably just because I yanked directly on the ribbon cable when removing the keyboard cable initially.

Sorry, this is maybe not the most productive thread :smile: