820-3476 no green light or ppbus_g3h

ytesfay80

Member
I am not getting a green light on the charger but I am getting 16.7 on ppdcin_g3h and 3.37v on pp3v42_g3h.
R7101 is showing 0.48v on pin 1 and 1.4v on pin 2. There is suppose to be 5v on the VDD pins in order to turn on U7100(ISL6259) so I troubleshooted to the U7190 area since that is where PP5V1_CHGR_VDDP is created.

I replaced U7190 with one from a donor board.

Here are some of the measurements I got from the U7190 area.

U7190 voltage | diode mode
pin 1 - 0.64v 0.688
pin 2 - 1.41v 0.003
pin 3 - 3.59v 0.361
pin 4 - 1.58v 0.004
pin 6 - 13.55v 0.56
pin 7 - shows 5v even though the schematic says it's a NC.

I replaced C7195, R7195, R7196 and C7198/C7199 with new parts from mouser. For some reason R7195 and R7196 both measure 155kohms even though they measured the proper resistance before I put them on the board. Is there something that could pull the resistance down?

I get a short to ground on both sides of L7195 and when I remove it and check for the short on the pads I get a short only on the Pin 2 side.
 

ytesfay80

Member
Also R7101 & R7105 measured proper resistance. R7105 showed 13.5v on one side and 10.8v on the other in voltage mode. the current sense resistors(r7121/r7122) weren't measuring properly so I just replaced them but that didnt solve the issue.

So U7100 is what could be bringing the voltage down from pp5v1_sw on U7190? I didn't know that was possible since it is separate diagram from the U7100 circuit on the schematic. Nice to know. I'll try replacing it later on tonight.
 

dukefawks

Administrator
U7190 powers the 5V to U7100 so yes it can pull it down. You need to check the resistors again as a shorted U7100 could have burned them again. First replace U7100 then the resistors.
 

ytesfay80

Member
Okay. I replaced U7100 and now I get a green light on charger and 15.5v on PPBUS_G3H(though schematic says it should be 8.6v).

I checked most of the power rails and these are the ones that were missing.
PP5V_S0 - 0.08v
PP5V_S0_FET - 0.08
PP0V675_S0_DDRVTT - 0.002
PP1V05_S0SW_PCH_HSIO - 0.079
PPVCC_S0_CPU - .022
PPVIN_SW_TBTBST - 0v
PP15V_TBT - 0v
PP3V3_TBTLC - 3.3v

I couldn't find which chip creates PP5V_S0 but I did see PP5V_S0_FET comes from U8080 and I was only getting 3.31v on P5VS0_EN(turns U8080 on) and 5v on PP5V_S4. Should I be troubleshooting P5VS0_EN?

Worth noting: When I first had this board 6 months I was just starting and I was testing the board w/o the heatsink on and the cpu would get hot so hopefully I didn't kill the cpu. Also, when probing around I caused u7700 to spark and it has a burn on the top of the chip.
I also see a tiny bit of blue corrosion next to U1900 so I don't know if that could be causing any issues here.
 
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dukefawks

Administrator
How can the CPU get hot if it doesn't even turn on? Yes corrosion anywhere can cause problems. A hole in the chip would of course mean it is dead. This board sound like a hell hole.
 

ytesfay80

Member
There is a slight misunderstanding.
The CPU doesn't turn on at all now but when I first got this board months ago it was working & getting hot and I was getting a fan spin but I wasn't getting anything to appear on the screen.
Then while trying to troubleshoot display issues I caused a spark things started messing up and I was getting no light on the charger or fan spin.

I will replace the burned U7700 chip and start troubleshooting. Where should I start looking in order to get PP5V_S0 working?
 

dukefawks

Administrator
U7700 has nothing to do with the board working, you can remove it once the boards powers up we'll get to that one.
 

ytesfay80

Member
Okay.
P5VS0_EN is showing 3.31v which is a problem. Should I check U8180 to figure why its 3.31v and not 5v?
 

dukefawks

Administrator
Why would an enable signal be 5V, it's a logic signal and is normally 3.3V. If 5VS0_EN is there then all other S0 voltages should be there and you should move on the check if CPU Vcore is there.
 

ytesfay80

Member
Sorry. I thought since the title had 5V in it that it should be 5v.

Anyways, I checked PPVCC_S0_CPU and got 0.022v.

If I have 0.08v on PP5V_S0 how is U7310 going to turn on in order to make PPVCC_S0_CPU.
 
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ytesfay80

Member
I got 0.111v on ALL_SYS_PWRGD. I also measured on R8162 and got 0.003 on pin 1 and 0.111v on pin 2. Also there is no resistor on r8162 as well as on my 3 donor boards but the schematic doesn't say that it is a no-stuff.

Could you explain to me what ALL_SYS_PWRGD does in the circuit? Thanks.
 

dukefawks

Administrator
Well, some voltage is missing. If S4 and S3 are there then everything should come on, besides CPU Vcore. Find the one that is missing, measure voltage on all coils first.
 

ytesfay80

Member
Well, some voltage is missing. If S4 and S3 are there then everything should come on, besides CPU Vcore. Find the one that is missing, measure voltage on all coils first.
When you say measure voltage on all coils which coils are you referring to?
PP5V_s0 is the rail that is missing. All the other s0 rails are present.
Is U8080 the chip that creates PP5V_S0? If so, should I try replacing that chip?
 

aprendiz

Moderator
What voltage do you have on PP5V_S0_FET? If you have nothing and have 5V on pin 1-3 and 3V on pin 2 from U8080 could be a bad U8080 or a short on PP5V_S0_FET line..
 
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ytesfay80

Member
I get 0.08v on PP5V_S0_FET and PP5V_S0.
On U8080 I got 5.147v on pins 1/3. 3.31v on pin 2.
I have the very thin fluke probes but I cant fit it inside on the U8080 pin for PP5V_S0_FET to check for a short. Is there any other way I can check for a short on PP5V_S0_FET.

Also, when I insert a usb stick and power on the board the usb stick lights up. I don't know if that adds to anything.
 
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aprendiz

Moderator
Pads for R5530, R5530 is not present but pin 1 and 2 are shorted on the board, here is where PP5V_S0_FET becomes PP5V_S0.........
 
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