this machine came to me as DOA and immediately found the issue as a 12v short to ground. Is it okay to inject voltage into that rail or does it have a potential path to the cpu or something?
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Flux and remove fuse @ F5200. Then power up again and measure the voltage to ground on pcb pad # 1 on the removed fuse @ F5200. Is the voltage present and stable? What is the voltage?
Then remove all power. Meter in resistance mode. Measure the resistance to ground on pcb pad # 2 on the removed fuse @ F5200. -
12.38v is stable on #1. direct short to ground on #2. 0.3 ohmsComment
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Inject 1 volt (not higher) onto the pin #2 side and test who heats up. If it is a capacitor, it will crumble / crack under the pressure. The fault may be the CPU but TBD.Comment
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was a bad capComment
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Board booting ?
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it boots
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hello everyone , working zebronics power suply 450 watts , 5v ,3.3v givin short to ground black wire, also in circuit at output, resistor was charred but shows right values , after removing resistors 39ohms, 51 ohms, there was no short , no continuity beeps with ground , but after replacing new resistors (now i am not switching it on) ,again short still exists . when i put bigger ohm resistor like 100k ohm , no short beeping sound comes , lower ohm resistor gives continuity beeps ,other big ones donest , as its a working psu , i am confused what to remove now or how to go further now .
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Hello everyone,
Firstly sorry for my english, french guy inside.
I brought a macbook pro A1708 - 820-00840 logic board, wasn't powering on.
History is a day, nothing happened when opening the laptop.
Nothing special inside, no corrosion, no liquid damage, never opened.
First, with the logicboard alone on the desk, mesures are :
5v017 and 0.000 amp. nothing else.
Finding a short on the PP3V3_G3H_VR, but not on the PP3V3_G3H (0.540 on diode mode), PPDCIN_G3H_CHGR_R present (5,1 volts) PPVIN_G3H_P3V3G3H around 4.1 volts. PM_EN_P3V3_G3H... -
Greetings to the entire forum, I ask you for help because I'm going crazy. A dear friend of mine gave me a macbook pro M1 A2338 that only works with an external screen. With the internal one, no backlight or image. Only the external display is detected from the system settings.
First I changed the display flat, then I made a backup with time machine and tried a reset in dfu but nothing to do, always the same problem.
I analyzed the logic board, it shows no sign of liquid or visible damage. I then moved on to examine the logic with the thermal camera and found that the UP701 chip was... -
Greetings to the entire forum, I ask you for help because I'm going crazy. A dear friend of mine gave me a macbook pro M1 A2338 that only works with an external screen. With the internal one, no backlight or image. Only the external display is detected from the system settings.
First I changed the display flat, then I made a backup with time machine and tried a reset in dfu but nothing to do, always the same problem.
I analyzed the logic board, it shows no sign of liquid or visible damage. I then moved on to examine the logic with the thermal camera and found that the UP701 chip was... -
Samsung UN55ES7003
made house call.
red power led comes on, blinks twice, no display, no backlight, relay clicks, repeat.
psu has self test feature.
disconnected from mainboard.
determined PSU ok BL ok.
suspect mainboard.
disconnecting tcon has no change on operation.
markings on mainboard:
BN97-06531P 0151
BN94-06123R
found and ordered replacement on ebay https://www.ebay.com/itm/394077328633
for 54$
second house call:
with replacement mainboard, tv turns on, has sound,...
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