Quoted from bluespin:
Williams system 6 & 7 boards used same sized connectors, so if you aren't careful you could fry a board on an older Williams game. That's why when you buy a system 6 or 7 game from an experienced collector they wil tell you to leave the connectors attached to the boards and to lay the head against the cabinet in transport, don't remove the connectors.
If you have the transporter that will allow you to leave the head on, that is great and it does save you some time when setting back up. And on a Williams 6 & 7 pin, that is a whole lot of wires if you have to figure out proper placement when going back together---if you did not take some good pictures before you took it all apart. Up top, on the CPU, there is one 4-pin connector and there are two 4-pin attachment points. If you did not mark that connector and you do not have the wiring manual you will play hell trying to figure out which position is correct because you can plug the connector to both attachment points.
I think the two connectors you are speaking of are the one white connector and the one black connector. If anyone wants to throw out daggers on crappy engineering, IMO, these two connectors take 1st Prize for dumb engineering. Both connectors are right next to each other on the harness;
Both connectors are the same size and they can be crossed plugged. This breaks all the principles when designing a wiring harness: Do not place two connectors of the same style next to each other on a wiring harness (No automobile manufacturer in the world will break this principle; You would not be able to cross plug any harness on your car---even if your life depended on doing so).
Not so with Williams.
The only thing that is different with these two Williams connectors is that one connector pair is white and the other pair black. And of you are a noo-b to Williams and do not know this black/white thing you can cross plug these two connectors----and you will fry a board.
With regards to the classic Sterns, even with properly keyed salmon-colored connector wafers, it is possible to cross plug a couple of these onto the wrong attachment pins on your CPU and LDA if you are not paying attention. But you will realize your mistake when you are looking a home for the connector you did not plug in. For example, you can have a 17 pin connector that is keyed on pin #3. And you can have a 15 pin connector that is keyed on #2. You can be off one pin and install the 15 pin connector to the 17 pin attach point. But then you will find your mistake as you are trying to find a home for the 17 pin connector.