Can someone explain exactly how/why this works.
https://www.youtube.com/watch?v=iy5k_f_UHnk
https://www.youtube.com/watch?v=iy5k_f_UHnk
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Got a case of something new weird at work. There is an old 2nd gen Intel i3 in an old “Pizza box” shell that has a small form factor power supply. Unfortunately I forgot to take pictures and model number off it.
Anyway, I get to work and get to look at this computer. Standby LED on the PSU is on, but the computer won't start. Hmm o.k. take the battery out of the main board try again, nothing.
O.k. then… unplug the power supply from the main board and put in a full size ATX PSU (yeeeesss! Exact that blown Powerman IP that I fixed a while back), plug it in and the old...
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Hi everyone,
I'm working on a MacBook Air 2020 (A2337, board 820-02016) and running into a strange USB-C issue. I've gone through quite a bit of testing and part replacement, but I'm stuck — hoping someone here can shed some light.
🛠 Original Issue
The machine initially wouldn't negotiate 20V over USB-C — stuck at 5V.
Diagnosis showed PP1V5_UPC0_LDO_CORE shorted to ground.
I replaced U3100 (UF400) using a donor board (A2179), and the machine powers on fine now.
⚠️ New Problem: One USB-C Port Only Works in One Orientation... -
Hello mates,
I bought this subwoofer a few days ago used and blind and it works erratically, as far as I could see, it has been tampered with, the speaker is not the original one and of 8 Ohm when it should be of 4, and there are some welds like reworked by the boards.
It doesn't have much power (expected more from it) and it distorts if you increase the volume over the middle, maybe it's because of the high impedance of the speaker. The problem is that it has sound when it wants, the led panels all work correctly, you can hear the power relay on power on, but right now... -
Hey ya'll this is my first post on here. I recently aquired a used/broken 2019 mbp 16 a2141 with the 820-01700 board. Seller told me that the laptop needed a new lcd. However upon doing some troubleshooting i found out the lcd is fine.
Laptop boots like a normal, plays chime, touchbar lights up however there is no image on the internal lcd. If i connect and external monitor while its already on, nothing happens and no image is displayed on external. However if i restart or boot the machine while its plugged in, the external then works and a backlight is now visible on the laptop.... -
Hi. I have been watching videos on how a power adaptor works.
There is explanation of the rectifier bridge to the pulse width modulator, the mosfet for switching, and opto-couplers, but there is little to nothing about the AC stage of the transformer the powers the primary coil.
So, I see that the PWM needs DC to work, but I don't see anything about how the AC gets from the mains supply to the transformer stage.
A transformer only works on AC so where is that part of the circuit.
I only see Capacitors on the output. Should I assume that the secondary coil and...