SOLVED: A1419 820-00134 27iMac no Backlight after connector DP_INIT_PIN_1 bent.

[it-solve]

Got this iMac with customer DIY replaced SSD, since then it turns on with no backlight.

Unlike the Macbooks, it doesn't seem to have backlight boost line on the main connector, only plain PP12V_LCD line. Not sure how bent pin on 12V lcd line can cause backlight failure. J8200 cable seems intact.

I reversed the screen connector and ensured that it has no short on the pins to the LCD.

Its very hard to test with screen on.

No short on any of the lines on the board or screen.
PP12V_LCD = 12V


Although no short on BKLT_BOOST_1

BKLT_BOOST_1 = BKLT_BOOST_2 = 0V (connected screen)
LED_RETURN_X = 0.2V
PP12V_S0_BKLT_PWR = 0V
F8100 intact

Randomly measured around U8100, no shorts

 

[2informaticos]

Do you get image for sure, only missing backlight?
What about DP_INT_EG_SL_HPD?

 

[it-solve]

Yes I can see the image and user login screen, no backlight

DP_INT_EG_SL_HPD - 3.29V

Also tried PRAM reset, no change

 

[2informaticos]

Check TCON_BLC_EN and TCON_BLC_EN_LED.
Be sure R4415 is good.

 

[it-solve]

Found the issue.



So resilient devices these non T2/Apple Silicon macs. This would have been corrupted firmware or blown IC with the new ones.

Thanks again