Hey,
Trying to revive old Macintosh SE.
Initially, it had one vertical line, solved by resoldering connector points on analog PCB.
Then vertical bars appeared, as you can see vertical bars cross the floppy icon and cursor.
Cleaned and recapped analog board, replaced ue8, and tested the continuity of suspicious traces.
After replacing ue8 with 74hc166 (the old one I think should be 74ls166), still has vertical bars and some flicker on the background.
The interesting thing is floppy icon and cursor are not affected by flicker, at least look different.
Then, by testing traces, accidentally found that when heating PAL IC`s UG7 or UG8, I get a clean picture, and it starts flickering after cooling down.
Tested again with old ue8 74ls166 - heating UG7 or UG8 does not affect the picture at all, stable vertical bars, no flicker.
In both cases, it has a startup sound.
I think UG7 or UG8 cannot be bad, as heating them with old ue8 does not affect the picture at all.
So now I am thinking, can it be 74hc166 is not suitable, and I should find 74ls166 because somehow the signal for UG7 or UG8 is incorrect with it, and after heating UG7 or UG8 somewhere, resistance increases, and it solves the problem temporarily?
Maybe any other ideas?
Trying to revive old Macintosh SE.
Initially, it had one vertical line, solved by resoldering connector points on analog PCB.
Then vertical bars appeared, as you can see vertical bars cross the floppy icon and cursor.
Cleaned and recapped analog board, replaced ue8, and tested the continuity of suspicious traces.
After replacing ue8 with 74hc166 (the old one I think should be 74ls166), still has vertical bars and some flicker on the background.
The interesting thing is floppy icon and cursor are not affected by flicker, at least look different.
Then, by testing traces, accidentally found that when heating PAL IC`s UG7 or UG8, I get a clean picture, and it starts flickering after cooling down.
Tested again with old ue8 74ls166 - heating UG7 or UG8 does not affect the picture at all, stable vertical bars, no flicker.
In both cases, it has a startup sound.
I think UG7 or UG8 cannot be bad, as heating them with old ue8 does not affect the picture at all.
So now I am thinking, can it be 74hc166 is not suitable, and I should find 74ls166 because somehow the signal for UG7 or UG8 is incorrect with it, and after heating UG7 or UG8 somewhere, resistance increases, and it solves the problem temporarily?
Maybe any other ideas?
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