History, symptoms: Came to me with leaky caps on the logic board. Replaced surface caps with tantalums, and repaired known bad traces.
The computer bongs on power up along with hard disk and floppy activity, but usually no video. Occasionally I will get a screen like the one shown. Adjusting the brightness changes how bright this pattern is, but I never see a sign of an actual video signal (eg no question mark floppy).
Upon inspection of the analog board, I found numerous cracked solder joints, which I have reflowed, to no effect.
I have chased down and/or swapped the usual culprits on the analog board (U1, R25, CR6) and the neck board (Q1), all seemingly good. Random checks of diodes, resistors, electrolytics on the analog board have not yielded anything. I have not checked the diode and transistor attached to the flyback shield, but that will be my next step. They appear physically intact and not overheated.
Do you think I may not yet be done with logic board repairs? I wonder if there are other bad traces that I have not yet discovered.
Thanks in advance for reading.
The computer bongs on power up along with hard disk and floppy activity, but usually no video. Occasionally I will get a screen like the one shown. Adjusting the brightness changes how bright this pattern is, but I never see a sign of an actual video signal (eg no question mark floppy).
Upon inspection of the analog board, I found numerous cracked solder joints, which I have reflowed, to no effect.
I have chased down and/or swapped the usual culprits on the analog board (U1, R25, CR6) and the neck board (Q1), all seemingly good. Random checks of diodes, resistors, electrolytics on the analog board have not yielded anything. I have not checked the diode and transistor attached to the flyback shield, but that will be my next step. They appear physically intact and not overheated.
Do you think I may not yet be done with logic board repairs? I wonder if there are other bad traces that I have not yet discovered.
Thanks in advance for reading.