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Iv'e been studying the construction of GM's ECMs, in particular the 7730 and 8707 models. I noticed something I found quite interesting. I have never seen a circuit board constructed with 4 layers of copper. I knew, and it was quite obvious that there was a printed circuit on top of, and below the ECM, and that the little circles of solder connected the two levels of circuitry. I noticed that some of those circles didn't have any traces associated with them, for about 10 minutes I was confused. Till I held the board up to a light and saw dark traces below the surface of the PCB. Thinking to myself, wow, 3 layers. Instinctivly I turned the board over and put it up to the light again, and I noticed that the dark traces on the front didn't match the dark traces on the back side. So I concluded that there is 4 layers of copper on a GM ECM PCB. Not only do they do that, they also dip them in a sealer to keep moisture out. I have to give GM a hand, they build one impressive ECM. Not to mension, these are ECM's from 88-93.
hehe
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