If you're reliably getting POST, I suggest it's not a DBE issue.I have seen pin 1 (DBE) on the 74ALS138 (IC59) try to have a signal but almost stays low, even though continuity is OK with the 74HC72 latch (IC77), and DBE on IC77 is fine, but strangely the signal is mangled. Maybe it's time for a new 74ALS138...
Have you done detailed physical checks on the traces on the underside of the board? By far the most cmmon fault with A300/A400 IME is that the board has been run over the central rear self tapping screw as it's taken in/out of the case, with can easily and quickly trash a lot of tracks all the way from the front to the back of the board.
Statistics: Posted by IanJeffray — Sat Dec 14, 2024 11:06 am