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820-2330 main rails voltages nighmare

I got stuck with a board 820-2330 no water damage, no visual damaged components, excellent physical condition. Did not have green light, PP3V42_G3H was shorted. The problem was U5727 which I replaced. Got the PP3V42_G3H back and green light on, but still not turning on. PPBUS_G3H was present, PP3V3_S5 was present but PP5V_S3 was missing. So I decided to replace U7201. After that, I lost the green light even when PP3V42_G3H was still present, PP5V_S3 was still missing and on top of that I lost PPBUS_G3H /not completely but it's only 1.7-1.8V/. This board for some reason has very complicated 1-wire circuit. I'll appreciate any tips. Thanks

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Deck the Halls
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Check PP3V3_S5 & PP3V3_S3. Put old U7201 back on. You were on the right course, but the problem was not U7201. PM_SLP_S4_L is missing because of a dead MCP79 and that is why PP5V_S3 is not turning on.

The signal from MCP79 going to Q7210 to keep the ENTRIP signal of U7201 low is not present. Remove Q7210 and see if PP5V_S3 shows up with old U7201.

Short on PP5V_S3 is always possible and something to check for, but I sincerely doubt this is the case.

Either way, this is old trash, I would junk it. If it is MCP79 you cannot find this anywhere new, just used, so you will have to do BGA rework and pray that the chip you get actually works. Further, this thing with a GPU is shittier than new machines with integrated graphics, and it is worth like $400 when it works. I would just toss it.

Also, double check if a short has appeared on PPBUS_G3H. 1.7v is the circuit going into a protect mode when there is a short on the bus, the charger will only output 1.7v instead of the standard 18.5v. My guess is in soldering the new U7201 that PPBUS_G3H got shorted to ground. There are two caps right next to each other for PPBUS_G3H & something else around U7201 that are really easy to short together. Clean the area of any flux residue and look at it under a microscope to see what happened.

P.S.

Even though you completely failed to fix this, you are actually using your brain to obtain the knowledge and resources required to solve your problem. You are making progress instead of waddling helpless, I hope others follow your example!

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Comments:

Thanks for the advice Louis, I completely forgot about ENTRIP signal from MCP. I remember you mentioned it in one of your videos. PPBUS_G3H wasn't shorted, with or without U7201, PPBUS_G3H voltage was varying between 1.7 and 3.8V. I am curious why there is no green light even when 3.42V is present? I guess U7000 is also defective

Anyway this board is an old trash as you said. I got it for spare parts and I was pretty sure MCP was bad because of the excellent physical condition, but since I found that PP3V42_G3H was missing I decided to give it shot and do a little training in case that was the only problem.

Can you refer me to a good source for genuine Amtech NC-599 flux. I found many sellers offer it for sale on ebay and amazon but it's fake Chinese clone

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notebookmechanix. ask ifixit to carry this

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Louis, these folks have some very good repair prices, are you sure you want to mention them? http://store.notebookmechanix.com

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I bet these prices are not the final ones and they are used to lure customers

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