Today I am working on Macbook Air A2179 2020 logic board # 820-01958-A. It turns on fine but no display. I see the amp meter taking amps from 0.14v to 0.18v (without the battery terminal attached). 20V is perfectly entering the motherboard. The CPU gets hot but no image at all. I am assuming it might be the backlight problem. Even I get ticks feels on the Trackpad. Lid volts 1.8 is all good too. Upon checking the backlight, I checked the 1st MOSFET Q8400, Pin 4 has 12v, this seems to be right but no output pins 1-2-5-6. Pin 3 which is LCDBKLT_EN_L also has 12v which is not right. On this pin it should be around 5.23v approx . I tried with another good LCD screen (just the glass), I use a torch behind, cannot seem to see anything. Any tips will be greatly appreciated. Thanks in advance
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Re: Logic Board 820-01958-A no display
Caps key led toggles? -
Re: Logic Board 820-01958-A no display
mon2, thanks for the reply... First thing I observed this, NO caps LED. But I checked the voltages on all inductor coils, they are present. What you think., from where should I start?? I was thinking it's backlight problem, but this maybe not it., ENABLE even is missing on the backlight chip, all other voltages are present. PRAM senses as when I do it the display on the amp meter resets too. So I know this is working.Comment
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Re: Logic Board 820-01958-A no display
Upon more trouble shooting I found that this rail PP3V3_G3SSW_SNS is missing, this is a TRUE 3.3V rail. It is generating from U8225. When checked U8225 (SLG5AP1445V). Pin # 2 is enable (SENSOR_PWR_EN coming from U7800 pin #152) & this pin should be getting some voltage like 1.8V ~ 3V but this pin is 0V & same with pin 7 (P3V3SEN_SS) out here too it's ZERO. Pin # 1 & 3 are correct 3.3.v (PP3V3_G3H). Can omeone could share their thoughts on this repair & check whether I am troubleshooting correctly. Thanks in advance.Comment
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Re: Logic Board 820-01958-A no display
CPU getting hot but does the fan spin? If yes, then you could check around U8500. I also got this board with the same problem but U8500 is shorted. After replaced U8500 I got display but no backlight. R8444/U8400 need to be replaced also to get the backlight.Comment
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Re: Logic Board 820-01958-A no display
Hey "anhbanxoi", thanks for your reply. There is NO fan spin at all. Even after a PRAM reset, no Fan Spin. I checked U8500 (MOSFET) & R8444, seems to be ok. & I think backlight circuit might be working, U8400 is not even getting the ENABLE signal at Pn 17 of this chip. The Caps Lock LED even does not light up & no Fan spin but I can feel that the trackpad is creating that ticking feel. Any more tips will be much appreciated. ThanksComment
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Re: Logic Board 820-01958-A no display
Try restore with Apple Configurator in DFU mode then check if you get ALL_SYS_PWRGD signal.Comment
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Re: Logic Board 820-01958-A no display
Thanks buddy... I am getting ALL_SYS_PWRGD signal 1.4V.. Think this voltage is ok or it should be 1.8V???Comment
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Re: Logic Board 820-01958-A no display
That is low. It should be 1v8.
Check the voltage to ground of PP1V8_PRIM_PCH.Comment
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.
The screen seems to blackout and stay black, but with a flashlight I can see the display.
With my Playstation 4 connected via HDMI, and running a game I can hear sound.
Assuming... -
Hi all!
This is my first post and also one of my first "deep dives" into electronic repair. I'm used to doing basic tasks with computers, like SSD/CPU replacement, thermal past re-application, etc. So here's the story...
I have a MacBook Air M1 that I bought to repair (I know, I'm weird; though I'm a CompSci major and want to learn more
, and it will not display anything on the internal display. I have verified that there's no backlight, as I booted the laptop and shined a flashlight on it and there's no display; it does completely boot up, and shows fine on an external...
11-04-2024, 06:36 PM -
Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic... -
I hope this is the right forum to post in despite not technically being a repair, but still a question of swapping boards.
I thought I'd explore the possibility to upgrade an existing working Samsung ue55nu7096u with the logic board (and power board if needed) of a newer model (ue55ru7105k) of the same size and appearance (and resolution). The reason being I'd like the extra inputs of that board including component in, an extra HDMI port and bluetooth. Its panel is broken so I have no use for the board otherwise.
The models launched in 2018 and 2019 respectively.... -
Hi all, I just want to share the repair of my 60PK550-UA TV set.
The TV set was powering on, just no image. After verification, nothing wrong on the YSus or ZSus boards. Nothing wrong on the main board either.
But I noticed that the LED was not flashing on the Logic Control Board. This is an EBR63450301. The LED is supposed to flash even with all the flat cables disconnected, with only the power cable attached.
All the voltages measured at the electrolytic capacitors on the board were good. From top left to bottom right:
C57: 3.30V
C61:...07-20-2023, 12:38 AM
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