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 #21   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 2 września 2017, 09:23 
R121 = 2.2M ?
One side of the resistance is mass-connected?




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 Tytuł: Re: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 2 września 2017, 09:23 
 
 
 
 #22   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 2 września 2017, 21:04 
Machine napisał(a):
R121 = 2.2M ?
One side of the resistance is mass-connected?

R121 measured -> 1.9MΩ
One side is connected to ground. Resistance between B of Q33 and ground 1.9MΩ.


Matic napisał(a):
Q33:
B -> 9.6V
E -> 10.1V
C -> 10.1V

Voltage VBE of this transistor is -0.5V which means that the transistor is in conductive state. VBE is only -0.5V, because base current is very low (high resistance of base resistor R121). Almost no voltage drop between emitter and collector, because current through the transistor is very low (high values of resistors R222 and R224).

I see no problem at all of this transistor.



 
 
 #23   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 30 października 2017, 22:59 
Hello!

I'm still working on this laptop. I ordered chips, which have arrived now.

Charger chip U101 (ADP3806) (on the board it is designated U42) replaced with brand new one -> Exactly the same issue
Power controller U61 (TB62506) replaced with brand new one -> still exactly the same issue.

Pictures of replaced chips (new chip are soldered on the board):
ObrazekObrazek

Any more idea please?



 
 
 #24   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 9 listopada 2017, 21:05 
matic napisał(a):
It also shuts down st-by power supply controller (tensions "VCC3M" and "VCC5M" disappears after pressing on the power button)

I made some measurements on st-by power supply controller U41 (MAX1901):
Voltages before / after pressing on the power button:

pin 4 -> 3.3V / 1V
pin 7 -> 2.5V / 0V
pin 8 -> 0V / 0V
pin 17 -> 9.8V / 4.7V
pin 20 -> 5.2V / 5.0V
pin 21 -> 16.4V / 15.9V
pin 22 -> 3.3V / 3.3V
pin 24 -> 5.0V / 4.7V
pin 28 -> 3.3V / 3.3V

I think that the issue could be voltage on pin 4 (signal "VCC5M_ON") after pressing on the power button.

Voltage on pins 63 and 64 of U61 -> 3.3V / 1V
Voltage on pin 76 of U28 -> 3.3V / 3.3V

Any idea, what else can I check?



 
 
 #25   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 14 listopada 2017, 09:25 
Check R866 = 10k.




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 #26   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 14 listopada 2017, 21:23 
Machine napisał(a):
Check R866 = 10k.
Resistance between pin 4 of U41 and pin 76 of U28 -> 10kΩ (I don't know, where this resistor is located).

Thanks for reply! Any more idea?



 
 
 #27   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 15 listopada 2017, 09:57 
Put a pin on pin 4 U41 and the other on U28 pin 76.
Measures the resistance by inverting the tips.




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 #28   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 15 listopada 2017, 22:17 
Machine napisał(a):
Put a pin on pin 4 U41 and the other on U28 pin 76.
Measures the resistance by inverting the tips.

Red probe on pin 4 of U41, black probe on pin 76 of U28 -> 10.01kΩ
Black probe on pin 4 of U41, red probe on pin 76 of U28 -> 9.98kΩ



 
 
 #29   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 16 listopada 2017, 15:04 
Probably short on U61 pin 63 and 64.
Replace U61.




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 #30   Tytuł: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 16 listopada 2017, 20:05 
Machine napisał(a):
Probably short on U61 pin 63 and 64.
Replace U61.


Like I said in post #23:
matic napisał(a):
Power controller U61 (TB62506) replaced with brand new one -> still exactly the same issue.

Obrazek




 
 
 Tytuł: Re: Re: IBM ThinkPad R52, Type: 1846, Doesn't power on with connected charger
PostNapisane: 16 listopada 2017, 20:05 
 
 
 
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