Hi Damien
I have done this before. Hope that this helps.
You have to pull almost all of the plugs off of the two boards and separate a lot of the cables in the bottom of the cabinet. It takes about 10-14 hours total in and out if you work slow and careful. I took pictures, wrote notes and marked everything I could. It went back together smoothly and works perfectly.
First you will need to get as much access as possible to the inner cabinet behind the playfield. If your game has only service posts, you can set something up outside of the game to support the posts well beyond the cabinet. I used a sawhorse with a 4x4 on top.
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The boards look like this to start. I took very detailed photos of each plug so there was no confusion when it went back together. Also you will probably have to weave the harness together to make it look professional, so photos will help there as well.
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Once you have the boards stripped, it will look like this. Couple of tips. The connectors are challenging to unplug. I found that a thin piece of styrene plastic slipped in under the locking tabs made it much easier to get them to release. Also since you are working and touching the boards (you may even have to unscrew the left side board to get the cables out) you may want to follow some static discharge practices/wear a static discharge wristband etc.
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You will then want to start disconnecting the cables in the bottom of the cabinet. I numbered and cataloged everything.
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Finally, you will be able to pile the giant bundle of wires you will have attached to the playfield up on the playfield. Like this. One person can lift it straight up and out, but it is a lot easier if you have an assistant.
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Basically reverse the process to install. Here is what my boards look like after reinstallation and weaving the harness.
IMG_1551 done (resized).JPG
Hope that helps and good luck!