Hello everybody, i could have some help.
I will note down the logic board number later if needed. Am away of the scope now and forgot it. It was the one schematics were never released for and so to substitute by a similar model.
The machine did fall a little less than half a meter. Plain, not on the edge. It looses lcd out on finishing the boot.
2 operating system tested. El Capitan and Catalina. To me it seems to be a gpu switching issue and I have no idea how to go on diagnosing.
On both OS it is avoidable by having an external display connected on boot. All normal. Output to LCD fine as well. No graphic glitches. No crashes on low and heavy usage.
Without external display the beaviour on finishing the boot is
Catalina:
Loosing video ( 3 seconds some stripes on the right and then black), backlight remains. Lid close / open or long press press or double tap power button or connecting external display brings back video out. Switching from integrated to dedicated and back to integrated is clearly visible. No more anomalies. No graphic glitches. No crashes on low and heavy usage.
El Capitan:
Loosing video. Loosing backlight. High fan spin. Plugging in external no effect / too late.......reboot...CPU panic report.
If I booted with external display and then disconnect -> LCD off, high fans, soon reboot. If I open e.g. cinebench and then disconnect the display all good. If I close cinebench -> you did guess it :-)
So the switch from dedicated to integrated seems to be the culprit here. I have no other display but to me it seems unlikely to be the reason !?
I thought about the famous CPU MOSFETS. Can we rule them out already ?
Help appreciated ! Do not want to replace all GMUX related chips on guessing.
best regards
I will note down the logic board number later if needed. Am away of the scope now and forgot it. It was the one schematics were never released for and so to substitute by a similar model.
The machine did fall a little less than half a meter. Plain, not on the edge. It looses lcd out on finishing the boot.
2 operating system tested. El Capitan and Catalina. To me it seems to be a gpu switching issue and I have no idea how to go on diagnosing.
On both OS it is avoidable by having an external display connected on boot. All normal. Output to LCD fine as well. No graphic glitches. No crashes on low and heavy usage.
Without external display the beaviour on finishing the boot is
Catalina:
Loosing video ( 3 seconds some stripes on the right and then black), backlight remains. Lid close / open or long press press or double tap power button or connecting external display brings back video out. Switching from integrated to dedicated and back to integrated is clearly visible. No more anomalies. No graphic glitches. No crashes on low and heavy usage.
El Capitan:
Loosing video. Loosing backlight. High fan spin. Plugging in external no effect / too late.......reboot...CPU panic report.
If I booted with external display and then disconnect -> LCD off, high fans, soon reboot. If I open e.g. cinebench and then disconnect the display all good. If I close cinebench -> you did guess it :-)
So the switch from dedicated to integrated seems to be the culprit here. I have no other display but to me it seems unlikely to be the reason !?
I thought about the famous CPU MOSFETS. Can we rule them out already ?
Help appreciated ! Do not want to replace all GMUX related chips on guessing.
best regards
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