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820-3787 short to ground on PP3v3_s5

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MaxFix

Member
This is a waterdamaged board with damage around the battery connector area. I get PPbus_G3h, green light on charger, PP3v3_s3 is there as well, but no _s4 power rails. PP5VS4_EN on U7501 is only 0.4 V. Also resistance to ground on PP3V3_S5 is 50 ohms measured from L7560. When i plug in the charger U1100 gets hot, so i suppose this is the culprit. Are these chips generic? or do i need one from a donor board?
 
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dukefawks

Administrator
Hmm, dead PCH :(. Start with replacing that first. BIOS will also need fixing if you get this board going again, but that is the least of your worries.
 
M

MaxFix

Member
Hey Duke, one more question for customer expectation management, from what i understand i will need a donorboard for the U1100, reballing etc. and after that what will still need to happen to the bios?
 
Gurmon

Gurmon

Member
if you can find a donor with the PCH and bios still on it, that is your first best option. If not, then its lottery if you get a good one from usual places.

Once PCH is replaced and board works, we can help you in fixing the bios.
 
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dukefawks

Administrator
You probably won't find a donor 3787 with a PCH still on it. Get a new PCH slap it on there and see if it works. Once it works the BIOS can fixed with a clean ME region.
 
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MaxFix

Member
I have a 3662 with the pch still on it, from a customer who did not want to continue the repair, i'll try that first.
 
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MaxFix

Member
I'm having trouble removing this chip from the motherboard with the bga machine, does anybody know the temperature needed to remove the PCH from the newer models?
 
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aprendiz

Moderator
The same as always, the only difference is that the motherboard is a big heat sink doing his job, just let it reach the desired temp and the chip should come out like any other...
 
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dukefawks

Administrator
If you have issues with removing this you need more practice. This should be quite easy and 3662 boards are not really practice material! Use some shitty MCP board for this purpose.
 
G.Beard

G.Beard

New member
MaxFix said:
I'm having trouble removing this chip from the motherboard with the bga machine, does anybody know the temperature needed to remove the PCH from the newer models?
Click to expand...

Are you using thermocouples to see what temps you are getting top side and under BGA?
 
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MaxFix

Member
We have practiced on easier boards, and have done multiple succesful gpu replacements, that's why it was a bit surprising. I'll let it bake a bit longer before trying to remove.
 
M

MaxFix

Member
So it's been a while, but we have finally received a 'new' pch from china. I slapped it on the board, and the short to ground is gone. The machine seems to respond to smc reset, but i am still not getting PP5VS4_EN, or any of the higher power rails.. does this have to do with the clean ME region that the smc needs? Or should the machine boot if everything is ok?
 
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