Very definitely, the soldering iron. Yours was the only one I have seen with so many IDE header legs unsoldered, and quite literally hanging in space - a total of 4 on one side and two on the other! Incredible, no wonder it didn't work.

Don't forget you can always flip back to 2 to enjoy "No Hang Playback" for a while.....
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One of the few remaining Mk1 owners... #00015