the computer will chime and the baclight comes on for a split second and then goes dark. i can see the image but the backlight stays off. could this be a faulty gpu?
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Last edited by kjchatman; 02-18-2022, 11:45 PM. -
Re: 2010 27" imac no backlight
If you can see an image, the GPU is working.
I believe this is a known issue with this model where the connectivity of the LED wiring becomes disconnected just inside the display.
I don't know if you've see this. It may or may not apply.
https://logi.wiki/index.php/iMac_bac...1419_and_above)
Check to see if the backlight voltage is at the main board even though the display is dark. If that's the case, you may need to do some internal wiring work on the display. There are some YouTube videos on this. -
Re: 2010 27" imac no backlight
the enable pin on the inverter board reads 1.5v. is that too low?Comment
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Re: 2010 27" imac no backlight
Typically that would be enough. Did you measure the backlight voltage on the logic board with the screen connected?
Be careful with the exposed power supply. There is not a lot of room to get in there. Maybe solder an extension wire that you can test with.Comment
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Re: 2010 27" imac no backlight
i fixed it. the inverter board had a short. can i upgrade to an SSD hard drive without using a 3rd part temperature sensor or will the cpu throttle?Comment
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Hello friends,
I have this unit with no backlight on screen. After inspection i determined there is a shorted capacitor on BKL_BOOST circuit. I removed the capacitor, short is gone but backlight still not working. I found that Q9702 is not open and R9721 is only around 70kOhms but according to schematics it should be 301k. I removed the resistor and connected the gate of Q9702 directly to GND. Now i have 12v passing by the mosfet to turn on backlight IC LP8561 (U9700) but BKL_BOOST circuit is not working. I can measure only 12V there but it should be around 60V.
Can you... -
this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
I bought this p2210f dell monitor to fix. Schematic is the same as p2210.
Behaviour is that monitors comes on but then backlight switches off almost instantly. If I look with flashlight I can still find the "No signal message". So definitely a backlight issue. Trying to advance the issue I proved that the protection circuit is switching off the backlight by shorting out C3 and resistor to disable the INL chip then re enable by removing the short.
This is where it gets interesting. When I disassembled the monitor to solder leads on c3 capacitor I noticed the backlight flickered... -
Hello all,
Am trying to figure out this backlight issue with this A1990 Macbook Pro.
Tests performed:
There is no backlight even with a good screen.
Backlight IC is receiving the correct support voltages.
Fuse F8400 ok
Current sense resistor R8400 ok
Backlight IC is receiving 3.3V on enable pin.
Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
Backlight IC receiving 5V from PP5V_G3S
Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
I2C_BKLT_SCL and I2C_BKLT_SDA both measure... -
Good evening guys, im new to this forum and searched around it to find a way to fix my broken imac 27 retina late 2015. Logic Board is 820-00292-A
Here´s the problem :
After i changed the blade ssd with an NVME SSD and accidentially bent some cpu socket pins (managed to get them straight up again, one pin broke but seems to be N/C) while trying to get some fresh thermal paste, i hear no chime and have no display. LEDs 1 and 2 are green but 3 and 4 not. I did some measuring and it seems that gfx_ok, is ok but dp_ok, is not okay. Checked some caps and diodes in circuit but everything...
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