thats correct, that red/black wire comes from the green Varta battery under the speaker panel. This PRAM battery most of the time has gone bad since the 90s and it's electrolyte fluid dropped down onto the main board, destroying other parts.

Man kann das I/O-board bei ebay finden, kostet nicht viel, der Austausch ist ja oben beschrieben, man muss da sehr vorsichtig vorgehen, zB das dünne, kurze Flexkabel ganz am Schluss.

I did a repair of this model, MacBook Air 13" early 2015, because the internal speakers didnt show up anymore but it was usable with headphones. So I carefully removed the I/O board and thoroughly and repeatedly cleaned the headphone jack with 99% isopropanol alcohol with Q-Tips and now sound came back to life. There is a little spring inside the jack that jammed.

right, also I often had problems with placing the audio panel back into its place, it's three little plastic noses just didnt want to fit back into its notches of the back.

gently, because there is this tiny green connector board with its two little buttons for PCMCIA cards ejection stuck in directly under it/ hold in place.

interesting, can you share a photo? my 166 doesnt have this..

yes, I had that problem on mine, too. One of the tiny 2,4 mm screws( red circles) was stripped, I couldnt get it out to renew the thermal paste under the heatpipe..

I solved the problem by using a plier, I grabed the stripped screw on its sides and that unlocked it..

I tried to use those ifixit spudgers with several powerbooks to lift the white plastic retainers but it's too risky.. tiny, fragile, brittle plastics. I now use regular L-shaped tweezers, much safer, more control.

these two screws are acually long screws.

I second this..