Replaced the processor. Everything is fine, but flash drives 2.0 do not work in one of the USB ports, but 3.0 works. Data lines 2.0 are not broken, but the resistance to data lines is different. The difference is 150 ohms. The resistance along the U2DN2_L line is 730 ohms, along the U2DN2_P line - 880 ohms. Other USB ports work properly. Could there be a problem with the processor? Removing the protective diode DS21 did not give a result, the problem is not in it. In Windows it displays with error message, when you put in flash drive there comes the same sound when you put it off and usb device dissappears in Windows. Any ideas?
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Re: LA-J812P USB 2.0 doesn't work
You need to be more clear with your observations. With "resistance along" you actually mean resistance to GND? If so, sounds awfully low already. If LS13 was already ruled out, same as with the resistors and caps on the USB20_P2 and USB20_N2 lines, then yes... you're likely dealing with a damaged AMD CPU.
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Hi all! I'm a newbie to to the forum and electronics repair in general.
I picked up a nonfunctional ASRock Taichi X570 motherboard that someone threw away. My main goal is it to repair and use it. But even if it's not possible, I'd like to learn about the process.
I'd very much appreciate some guidance.
Here are the steps I've taken to diagnose the board:
I first tried powering the board without a CPU or memory. The lights turned on. As you'd expect, the board wouldn't boot.
Hoping the board worked, I bought a compatible CPU on amazon. I wanted... -
Have functional A2485 unit, all things work but backlight is out.
There was some liquid corrosion around UP800's Caps and Res(s) - Cleaned all well . No change.
I measured resistance to ground of all UP800s surrounding components on another working board.
The components that are not correct on this board, with backlight out are:
CP810 - should have 250K resistance at Pin 1, its reading 80 Ohms
CP811 - Should have 25K at Pin 1, its reading 80 Ohms
RP805 - Should be 30K on both Pin 1 & 2 - Pin 1 is 50Ohms and Pin 2 is 200ohms... -
Hi guys, i was wondering, i've got 9Ohms on Vmem, one of the mosfet was shortet to ground, so i've desoldered hi and low mosfets nad still low res, then i removed all of the memory chips, and the resistance is still low, so did you had maybe a card with that low res on memories, and the card was working fine ?
Removed the U1866Q and still without result, i dont have thermal cam so can't see where is hot spot when incjeting voltage.
The resistance on core is ok 0.1Ohm ((Power 0.8V when on)
Resistance on 12V 4K ohms (Power present when on)
Resistance on 12V PEX 4K ohms... -
Hi, I'm Daniel, and I'm new to the world of repairing motherboards.
I would like to create a table, or more likely a guideline about the voltage rails and their possible resistance rail.
I know that the motherboard design has a very big depend on the rail's resistance, but I would like to know what is the smallest value for a rail that can be acceptable. For example, I heard that some new gaming motherboards can have 0,5 Ohm resistance on the GPU rail, but on an older type, it could be a sign of a shorted GPU rail.
So, I generated a table with AI so I can... -
I have a customer that brought in a Lenovo Legion S7 15ACH6. The problem is that the laptop is not posting.
My first thought was to take out the DRAM and put it back in.
No POST.
Then I swapped the dedicated RAM with good known working RAM.
No change.
I then measured to see if 1.2V was being generated for the memory to turn on, so I measured PL600 which is where the output of the 1.2V rail is.
Resistance was good; measuring ~40Ohms with the slotted RAM in.
I took the slotted memory out and measured again.
Resistance with...12-02-2024, 10:17 AM
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