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Don't have speakers for this. I did test them and all 4 are 4 ohms. Also tried just the right speaker and just the left. I feel like I'm missing something stupidly obvious.
Power rails seem fine, PP1V8_S0 is 1.8v and PPBUS is 12.59 at all 4 amp chips.
AUD_SPKRAMP_RESET_L is 1.8v.
One thing I noticed is. VREF_AMP_WL is 2v while booting and drops to 0 when booted up. Can't find datasheet on MAX98706, any idea what VREF_AMP_WL, VREF_AMP_TL etc do?
I'm really lost...
820-00281 board was liquid damaged. Corrosion around U7650 and U6400. Would not power on. Replaced a few damaged components around U7650 fixed the power problem. Now no audio through speakers. Audio through headphone jack works. U6400 had corrosion underneath it. Replaced U6400, problem...
Yes original charger.
Tested with new LCD, same problem.
Haven't checked backlight circuit voltages, don't want to put time into a potentially unrepairable problem and customer is considering purchasing a new one anyway.
Late 2013 13" 3476 board, backlight goes dim (can see video on LCD with flashlight) after 1-4 hours. Sometimes works fine for days on end. No sign of liquid damage.
Thoughts? I really don't want this thing on the bench for days on end.
820-2849 no sign of liquid damage. Powers cycles on and off for about a 1/2 second, during that time fan spins and all rails appear to be present.
Not much experience working on this board, I'm starting to think GPU is toast.
Any thoughts?
Thanks
820-4924 Liquid damaged. Replaced a few corroded caps and resistors, replaced burned LCD connector and LCD cable. Had no video internal or external, replaced U8300.
Everything working fine now except screen is black with backlight on and about 1" of faint vertical lines when waking from sleep...
Backlight works, get video to an external monitor, LCD just lights up black. No sign of liquid damage anywhere.
Not had one of these with this problem before. Poked around schematic a bit, not sure where to start.
Late 2013 27" iMac. No backlight, definitely has image on LCD. Checked pins 1-4, 2-5 and 3-6 on BKL connector, no voltage at all. Can't find a schematic for this board anywhere. Replaced LCD cable and reset PRAM, no change. Grateful for any help on this.
Couldn't find any burned or missing/broken components. Probably shorted something somewhere.
I knew this one was a long shot, don't know why I even took the job.
Thanks for confirming no info available.
Customer installed second drive in this 2012 Mac Mini Server. Said a metal clip near power supply came loose and touched the board. Now it powers on, no chime no video.
Wondering if anyone has any ideas as I cannot locate a schematic anywhere.