@zoneknud, The first thing to do, you already did; Remove all forms of power!
Next you’ll want to remove all boards (logic board and all daughters boards) and inspect both sides of them for burn marks, scorched or singed traces, etc. A loud popping noice is usually caused by a blown capacitor or a blown mosfet.
If you take your boards out and take some good quality, up close and high resolution pictures (remember good lighting) and update your question using [guide|21499|Adding images to existing questions], we can see what you see. This helps us in helping you