iMac a1419 I have the dark screen and the apple that you see with a flashlight pointed at it I have replaced the display connector various components but the screen is always black I understand that the black display connector does not reach voltage help me please
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Re: iMac a1419 820-3478-a no backlight
Hi. Are you still trying to repair this display?
If yes, share quality and detailed pictures of your display. Including the labels on the back side of the display.
Believe that you will have an aluminum shield with black tape and metal foil tape covering a logic board on the display along with a few screws.
This is called the T-Con board. Carefully remove the shield and share the pictures of the t-con board.
Before doing this, what is the history of when and why this screen went dark?
Confirm the back light connectors are not broken off the display. This the multiple black wire cluster from the imac. It mates with the display and fans out to drive usually 2 led strips.
If ok, issue could be the inverter power supply or the T-Con board itself.
We have repaired a few similar units in the past few weeks. Your issues may be similar.
T-Con boards can be replaced or repaired. Inverter boards are usually replaced.
Do you have a meter with capacitance checking? -
Re: iMac a1419 820-3478-a no backlight
On this machine backlight driver circuit is on the main logic board.
T-Con is unrelated to the issue since image is present.
First thing would be to try another display assembly if possible as a LED could be dead. Next would be measuring voltage on backlight circuit output, which is a bit tricky because it has to be measured across each pair of J8320 with the LCD connected and the board turned on.OpenBoardView — https://github.com/OpenBoardView/OpenBoardViewComment
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Re: iMac a1419 820-3478-a no backlight
@piernov - thanks! very nice to know.
As noted in another thread, we have stumbled across a nice shop on Aliexpress (MACSCREEN STORE) who has low cost stand alone tools to diagnose such panels and also replacement t-con boards.
They do not sell the backlight strips but they are available from other similar stores.
Are public schematics available for the main imac power supply and/or inverter boards used on A1312 or similar?
Learning as we go and wish to diagnose some of these bad boys. Thanks again!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... -
Hello all ~
Hope this finds you well. This LG 82UN8570AUD (April 2021 model) 4K UHD television has full audio capabilities but video is compromised / problematic.
When I picked up this large LG tv it had a full black screen upon startup. Previous owner said it just went black one day. No popping sound or anything else of note.
I got the display to work by taping off several traces of the right-hand side ribbon cable on the TCON that leads from TCON to PANEL. However, despite dozens and dozens of attempts to find the right combination / range of traces taped... -
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... -
Full model of the TV is 65UJ6300-UA.BUSYLOR. TV was given to me by a relative as non-operational so I'm trying to get it working so I have a nice cheap upgrade for my living room. This is my first TV repair so if it sounds a little like I know what I'm talking about, I don't.
TV turns on and has audio, but backlight doesn't turn on. Getting 230v from LED+ to chassis. Also can't see anything with flashlight test. Another forum suggested I replace the LED strips because that's the most common failure on LG TV's and the flashlight test doesn't always show results.
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boardview and schematic imac A1419 J17 MLB 820-3478
...11-12-2024, 04:14 PM
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