Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST
No I never got it working. I think the last thing I tried was injecting voltage onto PM_OPC_ZVM_L which did turn on the PPVCCEDRAM_S0_CPU rail. But the laptop still didn't boot. I gave up on it but I still have the board so if you figure anything out let me know!
I'm assuming the missing PM_OPC_ZVM_L is a symptom of what the real problem is, and not the problem itself.
reid
Member
Last Activity: 07-30-2023, 07:58 AM
Joined: 02-19-2011
Location:
-
Re: Dell 7280 Power Issues (LA-E122P)
I don't have the laptop anymore to check, but the part number should be printed inside the RAM slot area. You might have to remove some black plastic tape to find it, I can't remember for sure.
There's a few pictures that come up when you Google LA-E122P that show where in the RAM slot it is. Here's one from NewEgg: [URL="https://www.newegg.com/p/2S7-07JP-19NM3"]https://www.newegg.com/p/2S7-07JP-19NM3[/URL]Re: Dell 7280 Power Issues (LA-E122P)
I don't have the laptop anymore to check, but the part numberLeave a comment:
-
Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST
The machine could have a bad LCD, I've personally never seen this LCD work and don't have another logic board or screen to test with at the moment. Visually the screen flex cables look perfect and there's no damage to any LCD cables or connectors.
I think I'd need to remove the LCD to be able to connect it to the board outside of the case to measure the backlight voltage, unless there's an easy way to measure on the top/CPU side of the board... I definitely can't see the backlight turn on, and don't see anything...Leave a comment:
-
Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST
Thanks for the link! I think my board has a different problem. In Louis' video, the board still boots up and seems to work other than not charging the battery.
My board doesn't boot, but seems to charge fine. With the battery plugged in, I get around 1 amp on the USB-C at 20 V, and then it eventually increases to 1.8 amps. The board does respond to the power button, so it can be shut down by holding the button and even when off it still takes about 1.8 amps charging. When I said it was taking 700 mA before, that...Leave a comment:
-
Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST
It's 20 V. Starts out around 20 V, 750 mA, then goes down to 680 mA and seems to stay there.Leave a comment:
-
MacBook Pro 2016 A1706 (820-00239) No boot/POST
I'm working on a 2016 MacBook Pro A1706 with touchbar, 820-00239 logic board. The board seems to power on and takes about 700 mA from the USB-C port, the CPU gets warm, the trackpad clicks, but there is no chime and the caps lock light doesn't turn on.
The board is in good condition and there is no signs of liquid damage or any damaged components.
I've tried flashing a different BIOS - I'm not 100% sure if the file I flashed was good or if there is ME Region issues, but there was no change in the behavior at all. The SPI termination resistors all seem to be okay.... -
Re: Dell 7280 Power Issues (LA-E122P)
Good news!! I replaced the two diodes with some B0530W's that I found on an old 2008 MacBook donor board - they seemed to be close enough in spec. The laptop is now powering up successfully from the DC barrel plug, and the behaviour and voltages are pretty much the exact same when comparing the DC jack and USB-C power.
I'll probably order some RB751V-40WS diodes on Digikey, which seem to be closer in spec to the originals that are out of stock.
Thank you all very much for your help!!
For the sake...Leave a comment:
-
Re: Dell 7280 Power Issues (LA-E122P)
Looking closer at the circuit, +DC_IN_SOURCE connects to "DCIN" of the ISL88738 (PU901) chip through a SDMK0340L Schottkey diode, PD904. This reads as OL on both my meters.
There are two other diodes that also connect to "DCIN" of PU901, another SDMK0340L (PD901) that connects +PWR_SRC to DCIN, and a different type (PD903) that connects +VBUS_DC_SS (from USB-C power) to DCIN. When the USB-C power is connected, the cathode side of these diodes reads 19.5 V, and when the DC supply is connected, it fluctuates from...Leave a comment:
-
Re: Dell 7280 Power Issues (LA-E122P)
Interesting! So the 9 V seems abnormal since it's definitely not 1.7 or 3.3V.
I just removed and measured PR12 (499k) and PR18 (49.9k) and they both measure 1M on two different meters. I know I haven't changed those resistors.
The schematic I have is for a Rev 1.0 A00 LA-E122P, and the silkscreen on my board says the same thing. I've attached the schematic and boardview I'm using.
EDIT:
I looked at the schematic for the newer 7290 (LA-F312P), and PR12 and PR18 are 1M on that model, so I guess...Leave a comment:
-
Re: Dell 7280 Power Issues (LA-E122P)
Looking at the biasing for the FETs was very good advice!
USB Type C uses a similar transistor configuration, seemingly with PQ1213 = PQ9 and PQ1202 = PQ4.
On USB C, the gate pins are both 1.77 V, which appears to be correct based on the resistors used in the voltage divider. For the DC jack, the same voltage divider resistors are used, so I think I should also see 1.77 V on the PQ4 and PQ9 gates.
PQ9 has 9 V on the gate, and PQ4 has 19 V. When I measure PR16 and PR11 for PQ4, they seem to be the correct...Leave a comment:
-
Re: Dell 7280 Power Issues (LA-E122P)
Thanks, that makes sense. I’ve used Dell power adapters in the past that have had a broken ID pin/wire and the computer has always booted and displayed a warning about the wattage being unknown.
Here are some readings from those two MOSFETS. Does anything look out of the ordinary? I'll try to dig into that area a bit more, but I thought I'd post just in case something jumps out as being obviously wrong.
PQ9:
Pin 1, 2, 3: 19.5 V
Pin 4: 9.3 V, fluctuating
Pin 5: 19.5 V
PQ4:
...Leave a comment:
-
Re: Dell 7280 Power Issues (LA-E122P)
Thanks for the response and information! Here are the voltages those areas:
1: 3.4 - 3.5 V
2: 0.44 V
3: 5 V
4: 3.4Leave a comment:
-
Dell 7280 Power Issues (LA-E122P)
Hi, this is my first new thread and I am hoping to get some assistance troubleshooting a Dell Latitude 7280 (LA-E122P). I have fixed a few MacBook logic boards before, but I'm not familiar with Dell boards or schematics, so I don't really know what things are important to know or check first.
When I first got the laptop, it would not turn on. I'd plug it in and press the power button, the power LED would come on for a second and then turn off and the laptop wouldn't do anything. This was fixed by flashing the UC5 EEPROM, so I don't think there was any hardware issues when I first... -
Re: New Members - please post your introductions here
Hello, I have had this account for quite a few years and have gained tons of knowledge through reading threads on this forum. Thank you to everyone for being so helpful and willing to share information.Leave a comment:
No activity results to display
Leave a comment: