Lenovo Thinkcentre tiny M90Q gen 1 - no 12V rail
Hello Everyone,
Long story short, I got this unit for very cheap.
I've started to experiment with it's BIOS, as I did before successfully with an M900. However my very bad quality SOIC clip broken while dumping of the biosof and it must have damaged something on the panel, because it does not turn on, and does exactly nothing when powered. The maximum voltage that could have affected something is the 3.3 or 5v from the IC clip, because the unit was not powered while the bios dumping was in progress.
I've performed some measurements:
- 20V rail perfectly ok
- 3v3_S5 and 5v_S5 rails are ok
- The 3,3v rail which should power the SiO chip is not OK, there is 0v on that rail.
- As I've understood the schematic, that rail is connected to the 12V rail which also does not have any voltage.
Currently I am a bit stuck, Ive checked the capacitors and resistors around the FETs and the buck regulator, those are measuring OK.
PQ1103 which is the high-side MOSFET of the Buck regulator receives 20v, but there is no 12v coming out from this circuit. PQ1102 is the low side MOSFET, and the buck regulator itself is PU1101 on the schematic.
I've also found some interesting thing, there is a rail that is called 3V3_DWS, it is perfectly ok, but there are other rails such as the 3V3_DSW_G0, G1, G2.
G0 measures fine it has 3.3v, G1 has 0v, G2 has 8,37v.
These voltages (G1, G2, G0 is coming from a signal called SLP_SUS#) are connected to the 20V rail via a resistor so I guess these resistors are damaged.
I've uploaded the schematic and the boardview:
https://www.badcaps.net/forum/showthread.php?t=123548
Long story short, I got this unit for very cheap.
I've started to experiment with it's BIOS, as I did before successfully with an M900. However my very bad quality SOIC clip broken while dumping of the biosof and it must have damaged something on the panel, because it does not turn on, and does exactly nothing when powered. The maximum voltage that could have affected something is the 3.3 or 5v from the IC clip, because the unit was not powered while the bios dumping was in progress.
I've performed some measurements:
- 20V rail perfectly ok
- 3v3_S5 and 5v_S5 rails are ok
- The 3,3v rail which should power the SiO chip is not OK, there is 0v on that rail.
- As I've understood the schematic, that rail is connected to the 12V rail which also does not have any voltage.
Currently I am a bit stuck, Ive checked the capacitors and resistors around the FETs and the buck regulator, those are measuring OK.
PQ1103 which is the high-side MOSFET of the Buck regulator receives 20v, but there is no 12v coming out from this circuit. PQ1102 is the low side MOSFET, and the buck regulator itself is PU1101 on the schematic.
I've also found some interesting thing, there is a rail that is called 3V3_DWS, it is perfectly ok, but there are other rails such as the 3V3_DSW_G0, G1, G2.
G0 measures fine it has 3.3v, G1 has 0v, G2 has 8,37v.
These voltages (G1, G2, G0 is coming from a signal called SLP_SUS#) are connected to the 20V rail via a resistor so I guess these resistors are damaged.
I've uploaded the schematic and the boardview:
https://www.badcaps.net/forum/showthread.php?t=123548
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