[SOLVED] 820-2936 works only from battery, also not charging - "nice" 40sec video included.

[george-a]

[SOLVED] 820-2936 works only from battery, also not charging - "nice" 40sec video included.

Hi guys (again),

This one has been giving me hard time for a while now. It would only run from battery and after some testing with the charger connected it went kinda FUBAR. I replaced isl6259 and noticed that Q7030 was getting really hot and green light was gone soon after that (also replaced Q7035). Now having tested most of resistors and various points for shorts I removed F7040 and injected 12V on ppbus_g3h pin. If I now connect the charger the fan starts - its also quite funny to watch the system staying on when the charger is afterwards removed (video).

https://www.youtube.com/watch?v=pXYScevrZHU&feature=youtu.be

It seems the problem lies before the fuse but can't really focus on something.

Hope I am not wasting your time.

George

 

[aprendiz]

When apply 12 V on PPBUS_G3H if you connect charger and it powers on, this means one wire circuit is working.... Also the problem is not on PPBUS_G3H line.... The problem lies on ISL, maybe isl soldered wrong, replace ISL and output mosfets, also check sense resistors R7020 and R7021 should be 10 ohm each, measure resistance over pins 1 and 2 from C7020, should be 20ohm...... Measure R7051 (2.2ohm) and R7052 (0ohm), resistance over pin 1 and 2 from C7050 should be about 3-4ohm...

 

[aprendiz]

by the way, youtube video is set as private... I can't see it

 

[george-a]

by the way, youtube video is set as private... I can't see it

apologies for that: https://www.youtube.com/watch?v=pXYScevrZHU - should be ok now

thank you for your suggestions will do some testing today..

 

[larossmann]

What voltage is PPBUS_G3H without battery connected?

Does the voltage go up/down/change over time?

What is the resistance when you measure C7050 in resistance mode, no power connected?

What is the resistance when you measure C7020 in resistance mode, no power connected?

 

[george-a]

PPBUS_G3H, no batt, 1,9V now (was higher when I started messing with this board but fluctuating if I remember correctly)

C7050, resistance mode, 2,9ohm
C7020, resistance mode, 20ohm

 

[george-a]

OK I took this out of the box again for another try..

Measured R7005 at 170ohm instead of 20ohm and replaced it.

PPBUS_G3H is at 1.2V and L7030 gets REALLY HOT in about 30sec, diode measurement .414 - but EVEN hotter is D6990 in 10sec time, which I replaced to no avail.

Diode measurements at D6990: pin2=0, pin1=.234, pin3=.445 both old and new diode.

EDIT: [also replaced U6990 - its next in line so although I measured no shortcuts I though it might still cause some high impedance somehow]

Rabbit hole to hell or not?

 

[larossmann]

If R7005 is dead then U7000 is guaranteed dead.

Let's do one thing at a time here. Firstly, the diode mode measurements at D6990, are these across the diode, are these to ground?

Secondly, is PP3V42_G3H present?

Thirdly, is there a short to ground on F7040?

 

[george-a]

If R7005 is dead then U7000 is guaranteed dead.

Let's do one thing at a time here. Firstly, the diode mode measurements at D6990, are these across the diode, are these to ground?

Secondly, is PP3V42_G3H present?

Thirdly, is there a short to ground on F7040?

ok diode measurements to ground (new ones)

pin1: .428
pin2: 0
pin3: .544

PP3V42_G3H present, green light ok - EDIT: I dont let it stay on for long since D6990 gets really hot.

F7040 diode mode starts at .170 and rises slowly to .380 (keeps going one by one but Ill kill myself before it halts)

In the meantime I will replace U7000.


E D I T 2:

Ok it seems I was chasing my tail with this one... I replaced U7000 (again) and the fan spins... Will report back.

Can a bad R7005 destroy a new U7000?


E D I T 3:

it works!


god damn it.



thank you louis, thank you aprendiz.

 

[larossmann]

R7005 is just a current limiting resistor for U7000. It is not going to "kill" U7000. A bad U7000 will however kill a good R7005. U7000 does have a PP3V42_G3H pin so it was probably shorting PP3V42_G3H to ground, as well as CHGR_DCIN line which is why R7005 was blowing.

Glad you fixed it!