survivalbloke
Senior Member
Last Activity: Yesterday, 03:56 PM
Joined: 08-01-2021
Location: Maryland
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Need help pinpointing my short on this board (Lenovo) NM-D351
This is a Lenovo Thinkpad P15s Gen 2 with a board NM-D351. I'm having trouble finding my dead short to ground. I have the area narrowed down after much probing. You'll see in the boardview, there are two coils involved. I removed those coils and verified that that short is not on the mosfet side of those coils. . You'll see an arrangement on both sides of the board of 5 caps and one smaller one to the side. I have removed ALL 12 of these small caps and still have the short. Prior to that I injected at those caps with 1v5a and the short was only drawing 800ma so I could not see anything on thermal....
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Alienware M15 R3.Which of these is the BIOS chip?
This is a Alienware M15 R3. It has a no power condition, 0 amps being drawn. The power button is blinking 3 amber, 6 blue which lines up with an incomplete BIOS flash. Looking at this board, it appears it has 3 winbond chips and I'm not sure which of these is the BIOS chip. The board is LA-J52. Follow up question, can I extract a BIOS file from a Dell exectuable bios update file? ****EDIT***** That lower right "UE2" is not a winbond.
[ATTACH=JSON]{"alt":"Click image for larger version Name:\tM15.png Views:\t0 Size:\t2.13 MB ID:\t3235668","data-... -
Dell laptop powers up with kb backlight about 10 seconds, then shuts off
I've got a Dell Latitude 5580 which came in for no power. It's not exactly a no power issue though. The battery was puffy so I replaced that, but the symptom is that when the power button is depressed, the keyboard backlights will come on for about 10 seconds then go back off. Before depressing power button, I am drawing 112ma and oddly, there is no change in current draw once the button is pressed and the keyboard backlights illuminate.
Any ideas?Last edited by survivalbloke; 01-08-2024, 01:24 PM. -
mcplslg123[USER="149220"]mcplslg123[/USER] I was powering with a bench supply. I can usually hold my own here in the forums, understanding what I'm told, but I'm blanking out on your abbreviations S-G, S-D, G-D and ACDET/REGN. Can you dumb it down a little bit please? -
SMDFlea[USER="237374"]SMDFlea[/USER] Hey!
Laptop is HP 15-ay018nr and the serial number is CND6442K7J. The board is LA-D704P Rev 4.0Leave a comment:
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Thank you Master Yoda!...Leave a comment:
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HP 15-ay018nr LA-D704P. 20v to first mosfet, but 3v after
I'm curious as to what this is an indication of. I've got an HP laptop here with a slowly blinking caps lock key but no boot. The machine is alive electrically as it draws nearly 2A. I'm measuring 20v at the first mosfet input, but coming out of that mosfet I get only 3v. What is that an indication of?Last edited by SMDFlea; 12-28-2023, 04:53 PM. -
Resistance to ground is .1 ohms. I have looked closely at both sides of the board. Perhaps I just missed it....Leave a comment:
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Lenovo X280 - short on board, voltage injection pulling 4.9a but nothing heating up?
This laptop came in for no power. I saw the board was not taking any power so I pulled the board and began testing. As you see in the photo, on those pair of mosfets, I had 20v into and out of mosfet 1 and 20v into mosfet 2, but only 3v out of mosfet 2. I found a location which was shorted and injected 1v5a and it took all the current, but nothing is heating up with the thermal camera and I can't for the life of me figure out how 5a isn't showing on thermal. -
MacBook Pro A2141 820-01700 - stuck in 5v drawing 420ma
This laptop is stuck at 5v(all four ports checked) and exactly 420ma current draw. I checked PPBUS_G3H @ F7000 P2, and get ~8.76v where I should have 12.60v-12.65v. I checked resistance to ground @ F700 P2 and got an instant 0 which was odd. I applied 1v5a @F7000 P2 and have no draw, indicating no short.
I'm very confused. Send help.Last edited by survivalbloke; 11-28-2023, 02:19 PM. -
Macbook Pro A1990 - no power/ no draw
This device has logicboard# 820-01827. I couldn't find a schematic and bv for that one, so I am using a similar one, the 820-01041 which seems identical actually. Anyway I'm stuck on my troubleshooting, so let me take you through where I've been and where I am now and hopefully I can get some guidance. Initially the device was stuck on 5v.
I found C6503 shorted which is PPBUS_G3H. I injected 1v to reveal U7660 heating up. I replaced U7660 and that short/problem went away. (see images c6503, u7660).
After this I was getting 20v, but still no power draw/power on. I... -
Re: Need USB-C ports for LG 16T90P
I did not. The ones which I ordered from China looked identical to the ports on the machine. However, what I received was not what I ordered, and I ran out of time for the job.Leave a comment:
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Re: Macbook A2289 - backlight problems - have checked a lot already - out of ideas
With R8442 out, I get varying voltage outputs on EDP_BKLT_EN. Mostly 0 volts, but sometime .2 volts. Just to be completely sure, I removed the U8400, wicked all pads, cleaned and prepped pads - then replaced the U8400. 375c is no too hot for installing IC's like those is it?...Last edited by survivalbloke; 09-13-2023, 02:49 PM.Leave a comment:
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Re: What size is this resistor?
This had me laughing, not gonna lie!...Leave a comment:
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Re: What size is this resistor?
Sorry - here you are!...Leave a comment:
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Macbook A2289 - backlight problems - have checked a lot already - out of ideas
This is A2289, board 820-01987-A. It came in with the screen not working. We could not see any image on the screen, so we ruled out a backlight issue and instead replaced the panel. The display now comes up, but no backlight.
I didn't see any signs of liquid damage, but there was some odd looking spots around U8400. F8400 has voltage on either side of it, and I have 5v present on R8444 and R8445. I did not have 3.2v at R8442 so I figured U8400 was bad, and I replaced it. After replacement, a brief probe to R8442 showed 3.2v so I assumed I had fixed the device. After reassembly however,... -
What size is this resistor?
I'm used to seeing impedance specs which I understand, but I'm not understanding anything about this resistor besides the package, 0201. For reference, this is beside the backlight driver on A2289 macbook, board 820-01987....Last edited by survivalbloke; 09-12-2023, 11:13 AM. -
Re: Am I using my microscope wrong?
Thank you both. I flipped it over and now it's making sense!Leave a comment:
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Am I using my microscope wrong?
I've got a nice microscope to use, but I'm sort of a noob with microsoldering. I've gotten MUCH better over the last 6 months(with the help of this forum) but one thing is that I have sometimes struggled to get the scope high enough. You'll see in this image that I have the arm at its highest position possible, and I've also got the entire thing sitting on an old laptop for an extra couple inches.
So, there's that, which I just talked about, as well as the fact I hate the bulky base of this thing. I'd love to take it off the base and bolt it directly to my work surface. Maybe even... -
Re: Surface board, main rail shorted, can't find where
That was it - it was the cap right beside the current sense resistor. Thanks!...Leave a comment:
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