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820-2936 Green light, quarter fan spin.

J

JohnB8812

New member
Got a board in that was liquid damaged and got quarter fan spin. Nastiest areas were backlight fuse literally exploded, and it was really gross around the ISL6259. Measured voltages to start:

3V42: 3.46
PPBUS: 12.58
PPVRTC: 3.31
PP5V_S5: 4.99
PP3v3_S5: 3.3
PP3V3_S4: 3.3
PP3V3_S3: 0 volts

I decided to replace the ISL and burned resistors and caps around it: R7000, C7026, C7050, C7000, C7001, C7025. I still get a green light AND quarter fan spin, but now instead of one fan spin and nothing with PPBUS staying constant at 12.58 volts, I get constant quarter fan spins in succession and PPBUS jumps from 15 volts (?) down to 12.58 then to 3.9 and then jumps back up once the fan makes another spin attempt. Where would I look next to resolve this?

The only other area nasty on the board besides ISL was backlight towards top with a completely destroyed fuse also R5400 had lots of white nasty stuff on it. Other than that the only other part of the board coming into contact with liquid was Q7830 and R7830.
 
D

dukefawks

Administrator
To see if U7000 is working correct install battery and see if it charges.
Clock chip U2800 and R7402 are suspect for causing no boot.
 
smiba

smiba

New member
If PPBUS indeed gets to 15V you might want to check your soldering, especially to pin 21 of U7000.
 
J

JohnB8812

New member
Ok so checked soldering and touched up the top half of the chip on the Pin 21 side. It looks very well soldered now and I still get the same result. R7402: 90.9 K and the clock chip looks very clean even tho I would guess it could still be bad. HOWEVER, I did test with a battery Duke, and when I plug in the battery, the machine RUNS off of the battery with and without the charger plugged in. However the charger light stays green, and it doesn't turn orange. PPPBUS with just the battery plugged in and the machine running=11.91 volts.
 
D

dukefawks

Administrator
Resistance between pins 17/18 and 27/28 on U7000? Suspect dead resistor or corroded trace in the sense circuits.
 
J

JohnB8812

New member
Pins 17 and 18 34.26 M ohms and steadily falls
Pins 27 and 28 21.6 ohms and steadily falls

R7020 and R7021 10 ohms. Checking for burned traces around that area, but so far I don't see anything out of the ordinary. Would running this through the Ultrasonic before continuing be a good idea?
 
J

JohnB8812

New member
Update, touched up the soldering on R7051 and I now have 12.55 volts constant on PPBUS. However, I still get quarter fan spin to start up
 
J

JohnB8812

New member
Ok so I for sure have PPBUS and it does charge the battery. However, it still has quarter spin. PP3V3_S4 present, but PP3v3_S3 missing. Q7830 is the only other component that had liquid on it besides backlight fuse could this be causing 3v3_S3 to not work even tho it's an S0 fet?
 
smiba

smiba

New member
If you get a quarter spin you are actually moving into S0 for a little moment as the fan will only be activated in S0.

Will the machine POST (chime) on battery? If it does then your ISL circuit is still messed up. Otherwise see if you may have a short on one of the S3/S0 lines.
 
J

JohnB8812

New member
No machine does not post on battery. It does change the light from green to orange with a battery plugged in now, so i'd assume it's charging it. And will do on the power lines I'm pretty sure it's an S3 rail at this point as PP3v3_S3 is still missing
 
D

dukefawks

Administrator
Duke, and when I plug in the battery, the machine RUNS off of the battery with and without the charger plugged in.
You just said the machine ran off a battery.....what is going on here?

Replace clock chip to be sure.
 
J

JohnB8812

New member
Ok so I'm back to having the PPBUS voltage going nuts.

First, it would run off the battery but quarter fan spin when charging.
Then, I touched up the soldering and it got a steady 12.55 volts and a green to orange light with a battery plugged in.
Now, that has gone away and it's back to a green light only and a fluctuating PPBUS from 3.9 to 13.9.

I will replaced the clock chip, but I think something else is off here now. Would this have to be a corroded trace at this point? Because I don't get how PPBUS would work the way it should then all of a sudden stop. Bad ISL maybe? This board is starting to make me wonder
 
smiba

smiba

New member
Did you do the S3/S0 measurements like I said?

Again if PPBUS is moving around to way above >13V you most likely didn't solder it well, have malfunctioning mosfets (Unlikely, but feel if they're burning hot to make sure. Especially check the one for the low switching) or are having a broken ISL.

PPDCIN_G3H also heavily fluctuating?
 
Last edited:
J

JohnB8812

New member
Ok I'm gonna replace the ISL to rule that out since I have a several and then measure PPDCIN PPBUS and the S3/S0's.
 
J

JohnB8812

New member
Ok so new ISL and 100% properly soldered (I tested each pin lol).
PPDCIN: 16 volts
PPBUS: 12.55 volts (green to orange light with battery plugged in)
PPVRTC: 3.32
PP5V_S5: 4.99
PP3V3_S5: 3.3
PP3v3_S4: 3.3
PP3V3_S3: 0 volts
PP3v3_S3 diode mode: 2.97 k ohms
PP5V_S3: 0 volts
PP5v_S3 resistance mode (can't get an accurate enough reading for diode mode): 12.5 k ohms

All S0 rails missing.

I would guess the 5v_S3 rail looks most screwed up?
I have not replaced clock chip yet had to fix 3 iPhone screens and solder ISL back on. Would it be safe to replace that now?
 
J

JohnB8812

New member
Ok so I replaced the clock chip and Y2805 because a solder ball came out of it when removing clock chip. Still have green light and charging but still have quarter fan spin. What would be next thing to approach?
 
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