reformatt
Badcaps Legend
Last Activity: 06-07-2025, 06:13 AM
Joined: 02-17-2020
Location: Noosaville
-
I've also had a shorted cap after a diode on the 3.3V LDO on a HP board once. So it doesn't register as a short directly. Schematic helps if available. Use 1v voltage injection and camera on the LDO is a start.... -
Legend! Thank you, working great.Leave a comment:
-
Acer EX215-54 bios
Just need a BIOS password cleared off this one if possible. From an Acer EX215-54 with LA-K93P motherboard.
S/N: NXEGJSA0022110BA8B3400... -
You are on the wrong track. If there is no light on the charger, then the SMC will not enable charging. You would start with the one wire circuit (U7000 and U7001). SMC_BC_ACOK comes from U7100 and this must be high to allow Vcc for U7000. SYS_ONEWIRE comes from the SMC and is used to communicate with the charger and establish it's wattage etc. SMC needs that info to determine whether charger is suitable or not, so lack of signal here means no charging. U7000 is an over voltage protection device so you should see identical signals on both input and output. If that all checks out, then you would...Leave a comment:
-
Very helpful information, and thank your for sharing with the rest of the community. I wasn't aware that they had different sub-versions of the same model chip so this is something to be mindful of on any Lenovo in future.Leave a comment:
-
You can use the Rev 1 schematics, they are here on this forum if you do a search. Vcore rails would be those on pg 95 of the schematic. Measure at the coils PL1005, PL1006 etc. Should be around 1V or so. The presence of these indicate that all your other rails are ok, since CPU power is only enabled once all the preceding ones in the sequence are good. You won't get a display unless the CPU successfully POST's. Only takes one broken ball under the CPU for a signal to be missing, and the sequence stops. There is no link I can give you, as this is based on my experience on fault finding over many...Leave a comment:
-
In my experience, this very much sounds like bad balls under the CPU. Pretty common fault these days and I attribute it to the board being twisted/flexed when you open and close the lid from either side, rather than the middle. Only cure is to reball the CPU or replace the board. Forget reballing CPU's on Lenovo boards, even if you have the right gear to do it. They use a black glue which makes removal of the chip very difficult without damaging the pads on the PCB. Other vendors use soft glue material that comes off pretty easy with heat, so I'm not sure what Lenovo is trying to achieve with...Leave a comment:
-
It is possible to program a BGA EC standalone but the only one I know of currently is the SVOD4 with the debug PCB and BGA socket adaptor. This is 140 euro from their store, on top of the SVOD itself.
Only one I really trust on Aliexpress these days is SUHMSLeave a comment:
-
LA-N631P schematic and boardview request
This is from a 2024 Acer Aspire 15 N23C3. Unit has liquid damage but CPU seems to have survived. Can't find anything on this board, but have noted the following until a schematic becomes available.
PUA01 RT6543AGQW (ML=) [I]PCH +1V[/I]
PUZ101 RT3624BE [I]CPU Vcore[/I]
PU301 RT6338BGQUF (RW=) [I]+3.3V[/I]
PU501 RT6310CGQUF (S2=) +5.1V
PUM1 TPS51488 [I]RAM +1.2V[/I]
PUB1 Intersil 9238 B+
UVH2 EM5109-A [I]+3V LDO[/I]
UK1 KB9542QG EC
Main issues for this board are a hole in the PCH power IC... -
Good point. Some trackpad cables (like the one on the old A1534) were asymmetric, and had broad copper connections for the main power rail and ground. I once had a similar thing on that model because customer had torn the cable, ordered another but had put the cable in upside down, shorting all the data lines etc together on the other side!
On this one, you have 5 pins on one side for PPBUS_AON so that's the only thing that makes sense to me.Leave a comment:
-
Are you getting 20V negotiated on USB-C and what is the current flow? Check battery flex cable for corrosion etc, SMBUS lines to battery etc. Go to System Report/Power, is battery data reported? Service Recommended etc?
MAC OS doesn't report charging till about 1 minute after being plugged in, even though battery is charging.Leave a comment:
-
Being an A1990 it has CPU and GPU graphics and sounds like one isn't working properly when it's flipping from one to the other or or when the kext is loaded. The MUX chip comes to mind (U9850) as that's commonly damaged when you have liquid damage in the LCD connector. Might be a bad GPU.Leave a comment:
-
Don't have the schematic as it's behind a paywall. Did see a block diagram though, looks like this chip isn't programmable and gets it's code from a 256MB SPI flash chip.
...Leave a comment:
-
R5263 is also back to front on pinoutLeave a comment:
-
Just discovered this today. Working on a liquid damaged board, and cleaning up corrosion around UC300. The pin numbering is back to front in the schematic in the schematic for RC321, hence why its wrong on the boardview. I will refer to the pins as they currently are on the boardview.
CC328 pin 1 connects on the board to RC321 pin 1 not pin 2 (the bottom of the resistor, not the top). RC321 pin 2 connects to UC300/22 and CC329 pin 1.
CC332 also back to front on the pinout too...Last edited by reformatt; 03-27-2025, 10:24 PM.Leave a comment:
-
If you feel T2/BridgeOS are fine, then you would check all your voltages up to CPU Vcore are present during the Intel power sequence. Presence of Vcore indicates the preceding ones are present and that your PCH is likely ok. The EFI BIOS is part of the DFU restore and located on the NAND's so you can rule that out.
If the CPU is attempting to boot, you should see that in your USB-C current consumption (without battery of course). Would expect over 1 amp for this board on the bench when plugged in.Leave a comment:
-
Forgot about this thread. Are you still working on it? Do you get VSYS15 at all or is the main power rail dead? Have you checked it isn't shorted?...Leave a comment:
-
This model (and the A1990) often have corrosion on each wing on the board where the fan intakes are. I would inspect these areas closely for corrosion. Note DFU should be a last resort, not the first one. If you have an existing hardware issue, this makes troubleshooting so much harder as the DFU restore fails and you have incomplete or missing BridgeOS. So two faults and it makes it a lot harder. This used to be in the old RepairWiki notes, not sure about the new one.
Refer to the wiki for DFU errors:
[url]https://logi.wiki/index.php/DFU_Mode_Restore_(Macs)#DFU_error_codes_and_troubleshooting[/url]...Leave a comment:
-
Check SSD power rails for shorts. Common on this model. You might be in luck for it to be a shorted cap on the ssd power rails, as PPBUS_G3H isn't shorted as well.Leave a comment:
No activity results to display
Leave a comment: