Hi all,
I have a Lenovo Y580 board which works fine on battery power, and the battery charges normally with a charger. The issue is when the input is from the charging port. The charger used is perfect and is in use in another Y580 laptop
the 19v comes into the + of the charging port and enters the first mosfet PQ301. Voltage on the other side drops slightly (by .5v), and enters the 2nd mosfet PQ302. The voltage on the other side, and thus at the main power rail current resistor at PR301, is 0.9V. However, the main power rail is NOT short at this point (as also evidenced by the fact the board works fine off a charged battery).
Thinking this was an easy fix (the 2 mosfets mentioned above must be bad right?), I changed them over with 2 other p-channel mosfets (AO4435) off an old board, fully expecting the problem to be fixed, but NO CHANGE. Still 0.9v on PR301.
I then changed the battery charging chip PU301, which made no difference either.
I do have access to a good board, but couldn't work it out by comparing the 2.
What is clear is that on the good board, the voltage that comes through on the + of the charging point is identical to the voltage on the current resistor at PU301, so on the bad board, something is already wrong as the voltage drops .5v after the 1st mosfet
Another difference between the 2. On the good board, with the charger plugged in and the board off, 3 of the battery terminal pins have 3.3v as is common with many laptops and to be expected. On the bad board, these 3 pins have 0v. However, once the bad board is on using a charged battery, they then have 3.3v.
Could it be that I have been unlucky in my choice of spare parts (they too are faulty???). The board has the exact same symptoms and voltages before and after both sets of changes. (ie the mosfets and the charging chip)
Can anybody help me work out where the 19v voltage is disappearing to??
Schematic attached.
Thanks
I have a Lenovo Y580 board which works fine on battery power, and the battery charges normally with a charger. The issue is when the input is from the charging port. The charger used is perfect and is in use in another Y580 laptop
the 19v comes into the + of the charging port and enters the first mosfet PQ301. Voltage on the other side drops slightly (by .5v), and enters the 2nd mosfet PQ302. The voltage on the other side, and thus at the main power rail current resistor at PR301, is 0.9V. However, the main power rail is NOT short at this point (as also evidenced by the fact the board works fine off a charged battery).
Thinking this was an easy fix (the 2 mosfets mentioned above must be bad right?), I changed them over with 2 other p-channel mosfets (AO4435) off an old board, fully expecting the problem to be fixed, but NO CHANGE. Still 0.9v on PR301.
I then changed the battery charging chip PU301, which made no difference either.
I do have access to a good board, but couldn't work it out by comparing the 2.
What is clear is that on the good board, the voltage that comes through on the + of the charging point is identical to the voltage on the current resistor at PU301, so on the bad board, something is already wrong as the voltage drops .5v after the 1st mosfet
Another difference between the 2. On the good board, with the charger plugged in and the board off, 3 of the battery terminal pins have 3.3v as is common with many laptops and to be expected. On the bad board, these 3 pins have 0v. However, once the bad board is on using a charged battery, they then have 3.3v.
Could it be that I have been unlucky in my choice of spare parts (they too are faulty???). The board has the exact same symptoms and voltages before and after both sets of changes. (ie the mosfets and the charging chip)
Can anybody help me work out where the 19v voltage is disappearing to??
Schematic attached.
Thanks
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