820-2915 S3 PWR Cyclng

[SMMRepair]

So you powered the board on without letting it dry. Why?

Check clock first.

 

[dukefawks]

ALL_SYS cycling too? If not then there is a missing rail, either S3 or S0.

 

[Ryanlen2]

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.

dukefawks
Confirmed... All_SYS is cycling 3.3V.

 

[Ryanlen2]

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.

 

[Gurmon]

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 ?

 

[Ryanlen2]

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.

 

[dukefawks]

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?

 

[Ryanlen2]

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

 

[dukefawks]

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.

 

[Ryanlen2]

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!