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Have you seen or heard of temporary backlight at initial power up?

Replaced a few more caps on PPVOUT_S0_LCDBKLT_F after burnig up some more caps. DIode mode there is consistently 1.12 there. Now I'm getting backlight briefly on initial power up and voltage will remain at 54V then drops to 12V and then down to basically zero. KBD backlight voltages seem to...

Excellent info. Thank you! I'll fix that and see what happens!

I'm guessing another bad cap. would that be related or potential cause of LCDBKLT_EN_L: =12.6V?

Liquid damage to backlight area on board. replaced shorted cap C8462 and F8400. LCDBKLT_EN_L: =12.6V BKLT SCL/SDA= 5.1V BKLT EN R =3.3V PP5V_S0_BKLT_D/A= 5V DP_INT_HPD= goes to 3.3V R8450/1/2/3 all good resistance and diode values check out PPVOUT_S0_LCDBKLT_F = diode value is low at .12 -...

SOLVED: Replacing the CPU has resolved the issue.

My Medusa didn’t have proper file for this firmware.

Thanks for doing that. That bios works but the Mac remains incredibly slow most of the time so CPU is going to be swapped.

Correct

With your bin file, I only get first two LED's on MLB to light with display connected. It no longer posts.

ok I will try it

Let me know if you have time to clean the one at link I provided or do you know if yours is specific to 820-01134?

I have one that is right model number. I thought I attached to last post but guess it was too big. Link to bios file is here: https://drive.google.com/file/d/1HT_2Nrjg4n7c1y009XZcldr0L3Y0aea2/view?usp=sharing

Can you check this one for me?

Uh oh… that’s not good. That means I don’t have any copy at all anymore. Not sure how I managed that. I thought it saved successfully. I’m guessing you don’t have that bios? Not seeing any posts here for it

Obvious was the Hard drive but swapped to SSD, PRAM Resets, tried different ram just in case... I'm guessing it's either BIOS or CPU.. Would you be willing to see if you can fix the attached BIOS? My Medusa doesn't have the right file.

I ended up swapping the CPU and it has been working fine and waking normally and without kernel panics.

Hi there, if I let this iMac go to deep sleep, it either will not wake up from sleep or it will crash and restart. Sometimes the backlight comes on but screen stays blank. I believe I've seen this before a couple of times with this year/model and ended up with a new board and CPU to fix. Is...

Dah! good call. I forgot I had my tech try different display cable when originally screen quit working not sure exactly what he did but L8504 was visibly bad. Replaced and KB backlight is back. I'm happy to finally punt this mac from my bench! Thanks!

appears t2 is not sending PWM. I tried dfu restore and reloading. can i just send 3v3_S0 to pin 12 of u8400 so keyboard BL stays on when awake? I had a similar case with A1989 where keyboard backlight would be intermittent then eventually it was consistently on... seems like this might be...