(347) 552-2258 [email protected]

820-3476 1 volt on PPBUS_G3H

J

JohnB8812

New member
We got this board in with a green light turning orange but no fan spin. The board was liquid damaged around U7090, the bottom left corner of the board near Q7155, the SMC RESET IC, and BADLY by the ISL6259. Reflowed areas of corrosion and replaced almost any component left of the ISL as well as the ISL itself. I checked each individual pin for continuity throughout the circuit and all was good. Resistance between 17/18 and 27/28 is good both 20 ohm and 3 ohn measurements. The first time I did replace it, the ISL got SUPER hot, and I did not get a green light. I went ahead and replaced Q7180 and the ISL again and now I'm back to square one on the problem with a green light that turns orange with no fan spin and only 1 volt on PPBUS. Measurements below at the ISL:

DCIN: 18 volts
ACIN: 4.48 volts
BCACOK: 3.3
RESET_L: 3.3
17/18: 3.9 ohms
27/28: 20.9 ohms.

Any and all help is appreciated

Thanks
 
J

JohnB8812

New member
Charger U GATE is 5.5 volts and L gate is 50 millivolts. The SMBUS lines are both 3.3. I'm just making sure because I've replaced a lot of stuff so far, is this another bad ISL chip? Q7180 appears to be opening now as I get 18 volts on the source and 7 in the gate. And the ISL is not scolding hot anymore
 
J

JohnB8812

New member
There definitely was some corrosion near Q7155 and like I said the ISL and all components on the left of it were replaced because lots of corrosion.
 
D

dukefawks

Administrator
680 Ohm to GND on PPBUS is way too low. All the FETs and ISL6259 should always be replaced together as one kills the other. Also verify all traces to the FETs gate pin.
 
J

JohnB8812

New member
I'm confused now. I have replaced all of the components but something weird happens when I put Q7130 on the board. With just a new Q7180, ISL, and Q7155 my resistance to ground on PPBUS is many kilohms. HOWEVER, when I put Q7130 on the board, the resistance to ground drops to around 0.62 kilohms. I have checked continuity from 6 and 7 of Q7130 to the other side of the board and I get continuity.

In diode mode with Q7130 on the board:

Pin 2: 0.557 on or off the board
Pin 7: 0.128 seems really low compared to donor, normal measurement consistent with donor when off of the board
Pin 6: 0.499 on or off board

I checked my soldering, I have tried a few Q7130's from an identical donor and a few Air boards (don't have anymore Retina boards I can try), and each time I put it on the board, the resistance measurements on PPBUS and CHGR_PHASE go down. I have also replaced C7145 as it looked nasty. No short on that line or any of the lines that I can find unless I put Q7130 on the board. Is there anything else that can be causing this to go low? Don't want to put power through until I relieve that short or I want to know if it normally pulls the resistance down when on the board (doesn't seem like it).
 
J

JohnB8812

New member
Ok so black probe to ground red probe to the PPBUS fuse: 310 kilohms to ground.
Red probe to ground black probe to the fuse I'm getting about 20 kilohms. I would guess that means I have some kind of short?
 
J

JohnB8812

New member
With a Q7130 on the board:

Black probe to ground red probe to fuse: 20 kilohms
Red probe to ground black probe to fuse: 0.5kilohms
 
D

dukefawks

Administrator
Different polarity causing resistance difference so this is not something to worry about. Remove the fuse and see if PPBUS comes up, eliminate the system pulling it down.
 
J

JohnB8812

New member
Any ideas? I can't figure out what is up I get a low resistance measurement on the creation side, but if I put any voltage through either side, I get zero on the creation side and 0.010 amps on the system side. Could this be a blown internal trace? Nothing seems to get hot
 
D

dukefawks

Administrator
At 400 Ohm nothing will get hot as this is way to much resistance to let any significant current flow. I have no idea what is going on right now.

For testing, the board should be able to power on from a charged battery with the fuse removed. Need to short the power on pads of course.
 
You must log in or register to reply here.
Top