Chasing my own tail here for the last 2-3 days with that 1.42 GHz CPU swap. One RAM slot not displaying or usually causing a hang at boot (or soon thereafter). And yes, tried 12 different RAM sticks in that J20 slot which had all booted when in another slot - with zero problems.
IT HAD TO BE THE SLOT or the changes I’d made.
Well, maybe partially.
With any stick in the J20 slot, seemed to be a bit more side-to-side play with the stick in that slot, compared with the other slots. And I had tried so many different sticks there with no change.
After removing the motherboard today and really cleaning that slot, it booted a couple of times with no problem at first. Then on the third boot (after warming up a bit) no J20 RAM reported and the hangs began all over again.
Pulled some newer RAM from another MDD and put one in the J20 slot and it has booted without fail since then. I didn’t really have a bad stick of RAM… I did have a worn slot whose contacts (when warmed up) lost contact. And you can see in the pics below, where each stick of RAM has a very slight wear pattern / or very small indentation. Numbers 1 and 2 are older (been-around-awhile RAM) whereas # 3 is newer and has not been swapped around, in and out of different machines. (Very slight, hint of visible wear.)
This might not be your problem… but it might be.
As your machine heated up the other day / with the hard crash… even a tiny variation might expand over time. Check your RAM, up close. Clean contact points with a cotton swab and alcohol and try to find the least worn RAM stick to use in that J23 slot. And maybe… you won’t need to jerk every card or peripheral out, or away.
Yeah, I didn’t believe it either. All my RAM tested good in other slots and machines. One (or even three) new sticks of RAM is still cheaper than a new / used CPU. (OR NEW machine.)
Worth a try?
[Click on images for larger views.]