820-2936 No Power

brunomotter

Member
Hello. Got an 820-2936 here that got fried by knockoff charger. ISL6269 was fried, Q7030 and Q7035 also fried. SMC is fried like KFC. I replaced ISL, replaced both mosfets and verified all current sensing resistors near ISL. Also replaced D6990, U6990 and Q7080 as they looked suspicious. At the present moment I got SMC out of the board and am working on establishing at least 12.24V on PPBUS_G3H line. My readings are as follows:

Got 16.5V from charger DCIN
PPBUS_G3H varies from 0.3V to 2V after some time charger is connected, if I heat up Q7080 I get immediately 12.24V on L7030 and steady 3.3V on L6995. I'm stuck now. Tried injecting 12.5V on L7030, I get a sparkle but it does not drain any current from my PSU. Any ideas on what to look?
 

2informaticos

Administrator
Staff member
"Tried injecting 12.5V on L7030, I get a sparkle but it does not drain any current from my PSU"
Don't try to bypass charger stage in such way.
You still have to repair it, even the rest of board is OK (or not).

Start checking resistance between pins 17/18 and 27/28 of ISL6259.
Also post some voltages; pins 1, 2, 3, 9, 12, 13, 14, 15, 19, 20.
Post exact value (ohm scale, measured onboard) for R7080/81 and R7085/86.
 

brunomotter

Member
17/18 = 2.4Ohm
27/28 = 20.5Ohm
R7080 = 98K
R7081 = 61.4K
R7085 = 465K
R7086 = 331k

Voltages:

Pin 1 = 5mV
Pin 2 = 16.25V
Pin 3 = 3.86V
Pin 9 = 0V
Pin 12 = 228mV
Pin 13 = 229mV
Pin 14 = 228mV
Pin 15 = scaling up and down from 80mV to 400mV
Pin 19 = 5.06V
Pin 20 = 5.06V
 

2informaticos

Administrator
Staff member
Solve that problem.
Post diode mode to ground first.
If no short/low value, post U6990 voltages.
Check R/D6990...
 

brunomotter

Member
I replaced R6990 and D6990 before posting here because they were blown... I found a short to GND on ISL and its two mosfets which I replaced. The short on D6990 was cleared after replacing them and D6990 is not blowing anymore. Voltages for U6990(already replaced it twice) are:

Pin 1 = 1.204V
Pin 2 = 3.64V
Pin 3 = 12.30V
Pin 4 = oscillating between 15.95V and 16.22V
Pin 5 = 0V
Pin 6 = 270mV
Pin 7 = oscillating between 15.90V and 16.22V
Pin 8 = 3.71V
Pin 9 = 313mV
Pin 10 = 0V

Diode mode to GND on L6995 is 0.324(red probe on ground, black on coil) and OL (red on coil, black on ground)
 
Last edited:

brunomotter

Member
Yes, I checked C6996 and it's not shorted... R6995 is 1Mohm... Will take another look under the microscope on U6990 area...
 

2informaticos

Administrator
Staff member
You miss something there.
If all changed, must get 3V42.
Post again diode mode on L6995 and all voltages for U6990...

Also compare diode mode (several points) and voltages with an working board.
 

brunomotter

Member
Diode mode(red on GND, black on L6995) = 0.331

Unfortunately I do not have a working board of the same model here to compare now... If someone here got any and could share readings would be nice!
 

brunomotter

Member
U6990 voltages:

Pin1 = 1.215V
Pin2 = 3.61V
Pin3 = 12.47V
Pin4 = 16.84V
Pin5 = 0V
Pin6 = 0.457V
Pin7 = 16.83V
Pin8 = 3.6V
Pin9 = 275mV
Pin10 = 0V
 
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