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820-2915 S3 PWR Cyclng

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Ryanlen2

Member
hi.
So I got this board cheep but working. Just needed some touch ups (KB connector, SPKR Connector) . So I carried out the deed and everything was OK (booting/chiming). I proceeded to clean the areas that had flux left on them with toothbrush and warm water/Branson mixture. Then dipped those parts in alcohol and lightly scrubbed. Afterward blew excess liquid off with air compressor and followed with light heat from hot air station. Went to trun it on and I only get 1 repeating fan spin. i have PPbus at 12.56, PP3v42 at 3.42V, PPVINVIN_S5_HS and all s5 rails. But all my s3 rails are cycling. Vcore not showing up.
My gut tells me I got some solution under PCH that didn't fully evaporate, but not sure what to do. I ran hot flux under it numerous times and changed SMC with no change.

Thanks, Have a better day than Im having!
 
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Ryanlen2

Member
SMMRepair
Nah... i always blow off alcohol with high air from compressor and under BGA's. Then hit the board and under the BGA's from bottom of board with hot air. Usually works fine, LOL. Its not like I just got lazy and decided to plug it in wet! I will check in AM, SMMRepair. Thanks for your input. :D

dukefawks
Confirmed... All_SYS is cycling 3.3V.
 
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Ryanlen2

Member
Hello,

U2800
PPVRTC - 3.3
PP3V42 - 3.42
PP3v3_s5 - 3.3
CLK 25 1,2 - cycling
CLK 25 ENET - cycling
CLK 25 SB - cycling
CLK 32 _ RTC - Steady
CLK_25_T29 - cycling

Changed U2800

PCH Fucked?

Thanks. Have a good one.
 
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Gurmon

Gurmon

Member
Unlikely a bad PCH. B

I'm suspecting you took CLK measurements with a multimeter ?

i'd still suspect U2800 & include checking U6100 + termination resistors.

I probably wouldn't have gone down the running hot flux under PCH route on this. Do you have a UC you can run this through ?
 
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Ryanlen2

Member
Gurmon

I appreciate the help. I feel like a shit head over this...
To answer your questions... Yes, I only have a multimeter to check. No scope at the moment.
I do have an Ultrasonic, but Im not sure if I can trust it. It is a 180 dollar True Sonic. Havent used it much because I was suspicious that it may me doing more harm than good. But then again, now that I think of it maybe its because of the way I have been drying them. In your honest opinion, what do you think? Should I trust the True Sonic if I dry boards in oven?
I did soak the board in heated solution Branson/Distilled water and cleaned with toothbrush followed by Alcohol bath. But thats it so far.
I did change the clock chip.
To check frequency, is there a scope you can recommend that is not too pricey? Do I really need one? Will multimeter with frequency counter be sufficient? Sorry for the long reply, I just want to get this taken care of.
As I said, thanks for the help.
Have a good one.
 
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dukefawks

Administrator
No need to check any clock stuff on this one as it wouldn't even power up without RTC.

Are you sure Vcore is not showing up at all, not even a split second?
 
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Ryanlen2

Member
Hello Duke.
Measuring on both sides of L7510/20/30, Vcore doesnt show at all. Not even the slightest movement on multimeter.

Resistance on Vcore is 10.8 Ohms.

U7400
Pin 1 (CPUIMVP_VR_ON) cycling 3.3V
Pin 2 (CPUIMVP_TON) cycling 11.68V on pin 1 R7402. Pin 2 R7402 is steady 12.56V. <----------- https://photos.app.goo.gl/ndCizUj3l9nBRG3t2

Already changed R7402 and U7400
 
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dukefawks

Administrator
This could pretty much be anything. From crap under PCH to dead PCH to simply a knocked off resistor to worst case a dead CPU even. Go over all the areas you worked on.
 
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Ryanlen2

Member
I kind of think its something to do with PCH because when I cleaned flux from kb connector I may have gotten solution under it. Before cleaning, everything worked. I have a ton of 2915s with dead GPUs. Can I swap PCHs from a dead board with hot air station and maybe heat gun for bottom heat? Just a thought... Not sure how I would reball.
I am gonna look again for broken component first, hopefully its as simple as that.

If its just crap under it. Whats the best way to get to it??

Thanks Duke!
 
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dukefawks

Administrator
You will have better luck swapping the GPU to a board that has a dead one. But it will fail anyway, especially if it still has a 2011 date code GPU you are living on borrowed time.
 
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