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820-00164 no power, weird behavior on PPBUS-G3H

Jay

Jay

Member
This board had a short on it which was resolved by replacing C7371. Now I still have no power but on PPBUS_G3H I have 500mV and slowly rising up to 1+V. Never seen behavior like that so not sure what to do or go after next. Checked all points for PPBUS_G3H they all show the same number. When I disconnect power and a minute later reconnect it, it picks up where it left off, only dropping a few mV so the charge is being kept somewhere, just don't understand the behavior.
 
D

dukefawks

Administrator
Check resistance between pins 17/18 27/28 of the ISL6259. Also this machine should run from a charged battery is problem is simply with the ISL circuit.
 
Jay

Jay

Member
2.3 Ohm between 17/18, 19.8 Ohm between 27/28. No power from battery but according to the magsafe when connected it is still charging, percentage unknown.
 
D

dukefawks

Administrator
Unless the battery is known good and holds a charge this is no help. What is resistance to GND on PPBUS? Is the PPBUS fuse good? DCIN on ISL6259 getting power?
 
Jay

Jay

Member
Resistance to GND on PPBUS is 25 kOhm and climbing. Fuse (F7700) is good. DCIN on U7100 is 14.38V
 
Jay

Jay

Member
I measured all the points the BV highlighted when I searched PPBUS_G3H, a coil is not shown as one of those points. I also can't find a coil before the fuse in the schematic. The fuse is good though.
 
J

jadao

Member
You are maybe looking at F7700 whitch is another fuse for ppbus_g3h near backlight circuit.

There is another fuse right in the begining of PBUS_G3H it's F7140, and before this fuse there is a coil L7130, check the fuse and measure PPBUS on the coil and the fuse.
 
Jay

Jay

Member
jadao and dukefawkes I will check on your suggestions in a moment.

I found that F7140 was bad so replaced it, now get same 8.6V on both sides. Re-measuring the G3H line I run into a dead end at Q5500, I think. It has the right voltage coming in but is not shooting out PBUS S0 VSENSE to the SMC. The enable signal is coming in at 8.38V which is correct as far as I can tell.

L7130 gives me 8.6V on both sides.
F7700 also 8.6V on both sides.

Going to look for a Q5500 replacement and report back.
 
J

jadao

Member
If ppbus_g3h 8,6v is present and you have green/orange light, you should go further by checking other power rails.
do you have S5 power rails, S4, S3?
 
D

dukefawks

Administrator
Q5500 is just for voltage sensing and has nothing to do with power on.
So the PPBUS issue was a simple dead fuse, which makes sense after a short on that rail. Is the green/orange light present now? PP3V3_S5 present?
 
Jay

Jay

Member
Started measuring rails from scratch and hit a dead end at PP5V_S4RS3.
Leading this all the way back to the DC board of which I have tried 3, all resulting in no power.
I have no schematic for the DC board (820-3453-A) but there's a Cap that measures 14.87V on one side and 0V on the other side.... on all 3 of my DC boards. Don't know if that's OK or if all 3 of my boards are now f'd.

Attached is a picture.

Orange/green light still present.
 

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D

dukefawks

Administrator
Don't even need an IO board, these boards will power on without a green light so connecting only the power cable is enough. No need to plug in the flat cable.

No S4 can be absolutely anything and this board has history so it could be any knocked off component. As this was not water damage, physical damage is the most likely suspect. See if the 5V_S4 rail is pulsing, check PPVRTC.
 
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