HP Pavilion Touchsmart 23: Not turning on

[keerthi123]

Hi,

Trying to fix a HP Pavilion Touchsmart 23. and found that power (3.3V) comes to ON switch. Also 5.3V is available in some places. MOSFET were check and some of them are working. But not turning on and no power in buck converters near CPU.

In attached photo (this is near the power jack) in that buck converter. Top  MOSFET voltage is 19.6 and outout is 0V. Bottom MOSFET no voltages in S or D. Is this a problem with IC with lable "J8 FD H15"? The big aluminium colour component is a coil. What could be the problem. I check a datasheet for "J8 FD H15" and couldn't locate it.

Couldn't locate the schematic of the board.

Appreciate a support.

[perieanuo]

hi,
usually the supervisor IC test the outputs from shorts and if it's ok, he 'validates' the 19V
check all regulators from short and eliminate if you can
or just 'validate' yourself the 19V after identifying the correct mosfet and connecting D-S directly, the other one is for discharging.
if you find some voltage with short circuit, just inject that voltage from a good and powerful supply (that means something like 8A current capability, that's what it takes to burn a shorted capacitor) after disabling eventually the voltage regulator of your mobo.you're gonna have the surprise to see the damaged part popping up in 2 seconds.
seems risky, it's not, I've done it in a repair shop on lots of mobos with almost 100% success rate
sometimes I just bypassed the mosfet who validates the main supply and all came to life.but usually it was a short involved on some supply rail.in rare cases an regulator IC was to be replaced, but with some ic's this is not impossible.
study the datasheet of each regulator for good understanding on where you can inject the voltage and how to cut the regulator output on mobo
yes, it takes time.but 120 euros mobo also takes time...
regards,pierre

ps:
apparently it's not 19V validation issue, more a shorted small voltage power rail (you said you have some of the smaller voltages present).Identify which voltage is it, apply coresponding voltage, find shorted cap.finding the voltage it's not so complicated, trace the rail to the 'consumer' IC/module and then, that's your voltage (it depends on your finding, but not really complicated, may be prcessor or usb or whatever)

[keerthi123]

Thank you. I will follow rails again. Once I did it and not found any short to ground rails. I guessed that IC sent the trigger to MOSFET is bad. May be that is not the issue.