Bob, your memory is darn good! Based on your recollections of how the Original GM design was supposed to work when Sense line lost and since the circuit as shown didn't support observed operation, I decided to carefully examine an old GM unit. Low & behold, there are extra resistors and interconnect and one unexplained terminal (connection pad) on the integrated circuit at the heart of the module. I was able to trace out the circuit as shown in the diagram and then I could identify the "extra stuff". By the use of needle probes, I was even able to verify that this unit's output power transistor is still functional, and the IC is receiving Sense input and that the D2 input will increase slightly when Excite voltage is added. Out of the 3 that I mentioned, I still have one, but it is on a working tractor, so good sense tells me to leave it alone & not disassemble to see if it has some after market regulator, which I would bet on.
I also attached an old add (for Ford SS Ign) that I was reminded of because of after-market/original parts....for your amusement.
If you ever run across the GM Training materials & if it shows the IC internals, I sure would appreciate seeing it.
Been an interesting thread. Thanks all.
And yes, it goes without saying...I have too much time on my hands! Which is also how I knew what the inside of a Ford SSIgn module looked like.
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