reformatt
Badcaps Legend
Last Activity: Today, 01:33 AM
Joined: 02-17-2020
Location: Noosaville
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iCloud activation lock is linked to multiple hardware items on T2 and above, and not just linked to serial number. It was changed years ago by Apple due to some practices that China were using to bypass the locks on iPads. -
R8024 and R5400 are for current sense; it should just read as a short and aren't physical components. R8029, C8029 are NO STUFF in the schematic, so not fitted during production.
PP1V8_SUS is generated from U7800 (3 of 10), no where else. Check that resistance to ground at L8020 isn't short or low. Then check all your signals going in: PP3V3_S5, PP5V_PMICLDO, PM_SLP_SUS_L. Its a buck converter, so you also check the feedback components R8025, R8020, R8021, C8020. The PMIC shouldn't be underfilled, but if it got liquid damage under it, it may need to be removed and reballed....Leave a comment:
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PP1V8_S0 is derived via a load switch from PP1V8_SUS, which in turn is generated by PMIC U7800. Enable is PM_SLP_SUS_L (measure at R1458), output is via L8020. Check for low ohms etc on the 1.8V lines, especially around touchbar connectors.Leave a comment:
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Usually this data line is shorted after liquid damage to J8500. Should still boot, but you won't get an image. Very common fault....Leave a comment:
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The gas gauge line is BATT_SWI and is used to communicate with the controller in the battery. Absence of data on this line causes a panic condition and a reboot is asserted because of it. Can be either from a bad connection, broken pin or faulty battery.
My recollection from when I was doing these that it would at least boot to...Leave a comment:
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These batteries aren't intended to slide out. The battery is glued down, and the motherboard is then placed on top of the connector, and held down with adhesive. You either take it out or lift it up slightly with a pry tool to allow the battery to pop over the screw hole. Apple products are not designed to be repaired easily, and in fact come with a lot of booby traps for the uninitiated.
The reason it is boot looping as the iPad can't talk to the battery's gas gauge lines. Battery is either faulty or the pins on the motherboard side were damaged when you pulled the battery. On other...Leave a comment:
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From experience with liquid damage on Apple boards, you need to examine every passive component with dull grey end caps, as the pad underneath is often corroded (or the connection is bad). Often get boards come back with intermittent issues unless you do that. If the damage is extensive like you say, I write them off as the repair will bounce back to you. I just remove and replace from a donor en masse but I don't waste too much time on them.
First thing for me would be to replace the LCD connector and backlight IC (U7701). The feedback pin is often corroded (pin 5).Leave a comment:
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If the high side FET shorted, then you got 15V directly into the CPU. Pretty much game over at that point.Leave a comment:
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Check the I2C SCL/SDA lines to the battery. Fan will run at 100% if missing. Have seen this with a liquid damaged battery flex cable but could also be the connector itself.
Fan will also run flat out if tach is missing. Use MAC Fans control or similar to see if there is a tach present.Leave a comment:
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There are letters and numbers on the power sequence. Letter sequence is the state of the machine prior to power button press, and number sequence is after.
1D8V_S5 is i in the sequence, next is 1D8V_VCCIN_AUX is j. Power good signal from TPS51396RJER drives the enable for MP2941BGL (which you removed). This in turn drives APW8743CQBI (k). So the sequence stops at this point because of the missing voltage from your removed chip.Leave a comment:
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Power sequence is on pg 102 of the 19819-1 schematic - you start there. What reasoning did you have to remove PU5001? I would expect at least 1D8V_S5 on PL5301 which is prior to that in the sequence.
20V from USB-C is not overly important when troubleshooting as this machine uses a NVDC charger and it will boost up main power rail to roughly that of the nominal battery voltage when only fed 5V.Leave a comment:
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Just because you don't see an image on the screen, doesn't mean the system isn't booting up. The Touchbar itself is driven by a driver (kext) within MAC OS, so the fact you see 'ESC' on it indicates the board is booting. If the display is suspect, I disconnect it and run an external display by USB-C to HDMI adaptor to check. I also use the Chipmunk USB tester to confirm a boot.
CPU Vcore can measure as low 2 ohms to ground, this is not considered a short.Leave a comment:
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A dirty ME wouldn't prevent boot up, just make it quite slow to come on and boot.
My first thought is you got a faulty one (given it's from Aliexpress). These are generally salvaged off junk boards that don't work (they have no way of knowing they work or a means to test them either). I think the MO for these sellers is that you will think its too much hassle to send back and they keep your money, or they will blame the issue of it not working on you. Aliexpress these days make shipping back anything quite easy though and they generally side with the buyer. So I guess this is just...Leave a comment:
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I would've said faulty screen would be the most likely.
As far as the connector goes, parametric search at Digikey can point you in the right direction. Not sure what the point of the video was, but it doesn't help too much. I can at least see its a front flip right angle surface mount FFC.
You add number of pins, pin pitch, top/bottom/both contact pins, cable end type (straight, notched, tabbed) into the parametric search and see what matches.
[url]https://www.digikey.com/en/products/filter/ffc-fpc-flat-flexible-connector-assemblies/399?s=N4IgTCBcDaIG...Leave a comment:
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Sent him the latest exe via PM, so as not to clutter up the forum.Leave a comment:
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Appears that 3D3V_LCDVDD_S0 is missing. Should be enabled by power switch U5501. Check for 3D3V_S0 on pin 5, and eDP_VDD_EN_D on pin 4 should go to 3.3V when the system is booted. This may be subsequently disabled if communications with the screen are not established.Leave a comment:
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Does it happen with drag and drop? Have you tried other .bin files? Can't reproduce it on my end.Leave a comment:
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BIOS password on newer Lenovo's is in the embedded controller, not the BIOS chip. There are some removal methods, but it depends on what EC is on the board.
You'll will have to open it and determine what motherboard is fitted, or what EC is installed and go from there.
Review this thread:
[url]https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/bios-requests-only/3237235-lenovo-thinkpad-ec-pwd-bypass[/url]https://BIOS password on newer Lenov...ontroller, notLeave a comment:
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22uf 25V 0805Leave a comment:
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