Description of problem
Won't turn on or post, no fan spin
When I plug in the DC jack, the power light comes on for half a sec then goes off.
If I try to turn on by DC power, the orange power light (lightning icon, not power button) blinks 8 times
If I try to turn on by battery power, the same light actually goes solid blue for 2-3 seconds, then flashes at least 8-10 times, then the light goes off, still doesn't turn on.
Schematic of laptop
https://mega.nz/#!QZQAwRxD!_J2GCZ2Fo...LJ-U4Ce5R-eonE - HP Probook 6550B motherboard is 6050A2326601-MB-A02
What I've checked
I did try to short the mosfet, and power was pushing through to the second mosfet now, and then I injected power into the board with my DCPS, however it wasn't taking any amps and still not powering. My very limited understanding tells me that if it's not pulling any amps, then it's not a short and that the mosfet is shutting down as a safety feature, but I'm unsure what to look for next.
The DC jack circuit doesn't push power past the first mosfet, the battery circuit does. Neither turns on the computer though.
I have checked the Super IO (it's called IO Power in power diagram "TPS51218") it's listed as U25 IC, I get 0 voltage on any of those pins (it's 11 pin)
Next thing I measured is the KBC_PWR_ON which seems to lead to "TPS51125" IC
I get VREG3 - good
VREG5 - good
VIN - good
pin 23 is PGOOD, I get no voltage on that pin
There is a SPI Bios chip (cn11/MXIC MX25l6) it is getting 3.3V from 3VAL line, so I think that one is okay. There doesn't seem to be any 5v line to the bios chip
Won't turn on or post, no fan spin
When I plug in the DC jack, the power light comes on for half a sec then goes off.
If I try to turn on by DC power, the orange power light (lightning icon, not power button) blinks 8 times
If I try to turn on by battery power, the same light actually goes solid blue for 2-3 seconds, then flashes at least 8-10 times, then the light goes off, still doesn't turn on.
Schematic of laptop
https://mega.nz/#!QZQAwRxD!_J2GCZ2Fo...LJ-U4Ce5R-eonE - HP Probook 6550B motherboard is 6050A2326601-MB-A02
What I've checked
DC power mosfets
So if you have the schematic on Page 5, top right "JACK1" I get 19V at the dc jack, then over to the first mosfet Q533, I get 18.8v at the gate, 19.2v at the source, and no voltage on the drain.I did try to short the mosfet, and power was pushing through to the second mosfet now, and then I injected power into the board with my DCPS, however it wasn't taking any amps and still not powering. My very limited understanding tells me that if it's not pulling any amps, then it's not a short and that the mosfet is shutting down as a safety feature, but I'm unsure what to look for next.
Battery power mosfets
The battery power mosfets act differently, on the first mosfet Q13 source I get 11.2v(same as batt voltage), 0.1v at the gate, 11.2v on the drain, and power reaches the second mosfet, and I get 11.2V on both side. The DC jack circuit doesn't push power past the first mosfet, the battery circuit does. Neither turns on the computer though.
V5AL/V3AL/VIN
I've checked the Votlage Regulator IC. I get 5V on the VREG5 line and 3.3V on the VREG3 line, and get 18V at VIN. So the VIN, V5AL and V3AL are all present!Further checks
I definitely get 3.3v on power switchI have checked the Super IO (it's called IO Power in power diagram "TPS51218") it's listed as U25 IC, I get 0 voltage on any of those pins (it's 11 pin)
Next thing I measured is the KBC_PWR_ON which seems to lead to "TPS51125" IC
I get VREG3 - good
VREG5 - good
VIN - good
pin 23 is PGOOD, I get no voltage on that pin
There is a SPI Bios chip (cn11/MXIC MX25l6) it is getting 3.3V from 3VAL line, so I think that one is okay. There doesn't seem to be any 5v line to the bios chip
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