[SOLVED]820-3437 no power after surge

ytesfay80

Member
This machine was sent in as not working after a power surge. When I plug my chargers in I get no light at all and no fan spin even after plugging in a know good io board/cable. On the board I see some probe points that look discolored but I don't see any corrosion anywhere nor any damaged components so I can't say for sure there was liquid damage. A few of those discolored probe points were around the SMC and ISL6259 and other places.
There is no voltage on PP3v42_g3h or PPbus_g3h and no short to ground on either of those lines. Here are some other measurements I took on the DCIN line.

R7010 and Pins 1/2 of J7000 - fluctuates from 0.19v-0.47v
R7010 in diode mode - 0.70v - Resistance 100kohms

R7005 0v on both sides and no short to ground

I don't have a fake chinese charger to test and see if it turns on with it.
 
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dukefawks

Administrator
What is the first voltage to check if there is no green light?

Oh, I see no 3V42. Do you have a bench PSU to put 16V on DCIN?
 
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ytesfay80

Member
Okay I used my r mete ps305-dm power supply and tried injecting 16v into pin 1 of J7000 but the highest it would let the voltage go up to was 1.6v. The current was showing 5.02 Amps or mA it didn't specify which one and a red light was on the current side which I believe meant that was the highest it could go up to. Even with the charger plugged in the voltage would show around 1.3v on PPDCIN
 

2informaticos

Administrator
Staff member
Start injecting with lower voltage; go up from 1V for example.
If your supply shows 5A and gets blocked will not inject anything.
Put amp at max and increase voltage maintaining current less than 5A; if this is the limit of your supply...
 

ytesfay80

Member
I found that Q7180 was gettting really hot and that is where the short was. I replaced it with one from a donor and when I plugged the charger in still no light and DCIN voltage is around .1v so I went to inject voltage and Q7180 was getting very hot again.
 

2informaticos

Administrator
Staff member
Q7180 has no pin connected to ground.
Something more is shorted to ground after it.
You probably burnt it again.
Find the short before power up the board again.
Maybe Q7130...
 

ytesfay80

Member
The ISL6259 was not getting very hot but it did feel somewhat hot but I figure that could have been because Q7180 is on the other side of the board and the heat came from there.
I couldn't find any other component that was getting hot except for Q7180 so I just removed Q7180 and put 16v on that line but my power supply showed 0Amps going through it. I then cut off the power supply and plugged in the charger but there was still only 0.1v on PPDCIN_G3H.
 

2informaticos

Administrator
Staff member
I already told you start with lower voltage!
Increase voltage maintaining under the current limit of your supply...
Did you check Q7130?
 

ytesfay80

Member
Okay I put Q7180 back on the board and put 1v on that line and slowly went up to 1.6v which was the limit before 5 Amps was reached. I wasn't able to find any other component that was getting unusually hot. I even poured some alcohol to see what gets hot and sizzles away but nothing was sizzling when I put the alcohol on the board like Q7180.

Q7130 was not feeling too hot or burning the alcohol off fast.
 

dukefawks

Administrator
The 5A is just passing through Q7130 and heating it up. I bet PPBUS is shorted or there is a short after Q7130. That 5A is going somewhere.
 

ytesfay80

Member
Pin 2 of F7140(PPBUS_G3H) in diode mode was 0.159v and the resistance to ground was showing 445ohms.

I measured Q7130 in diode mode. Pin 1 was 0.61v and on the board there are 3 pins above it but on the boardview it doesn't show those 3 pins. All three of those pins measured 0v to ground in diode mode.
When I checked those same pins on Q7130 on a donor board I have they were showing about 0.61v in diode mode.

What do I check to find a short after Q7130?
 
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dukefawks

Administrator
445 Ohm on PPBUS is no good but not enough of a short to pull 5A. You need to find a real short, that 5A is going somewhere.....
 

ytesfay80

Member
So I thought it might have been C7130 that was getting hot but I couldn't tell if that heat was coming from Q7180 being close by so I just removed C7130&C7131. Before removing in diode mode both sides of C7130/C7131 were 0v to ground and after removing them Pin 1 is 0.57v in diode mode. With those components removed from the board I tried injecting 1v to the DCIN line but no current was going through.

Should I put another C7130/31 and Q7180 on the board? I just don't want to kill those components again.
 

2informaticos

Administrator
Staff member
R7120 short to ground?
If yes, check C7130/31 and C7135-37.
No other reason, as you have 0.159 at PPBUS_G3H; which is correct value there...
 

ytesfay80

Member
Okay I put a new C7130/31 on the board and now it turns on and I was able to boot my USB OS. The battery is not being recognized and shows the X. I plugged in one of my non working batteries I had laying around and it was recognized but wasn't charging which is likely because of that battery so I will order a new battery and this should be fixed.
This can be marked as solved.

Thanks 2informaticos dukefawks
 
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