HP 15-F233 motherboard no power

[Mo7babel]

Good morning all
I try to repair the motherboard of an hp 15-F233 (model 8UC), I got the diagram and the boardview but I did not locate the problem.
symptoms :
1. by plugging in the charger the led sometimes it lights up sometimes not.
2. by pressing the power button, the HDD LED lights up briefly and then goes out.
looking back on the motherboard:
the 19V ok
the 3.3V is ok when the charger led is on, but it becomes 5V when it is off.
by pressing the power button, the 5V is established and then returns to 0.
I believe that there is a short circuit but I cannot locate it.
if anyone can help me, i would be very grateful.
thank you

[lapfix]

Re: HP 15-F233 motherboard no power

Use diode mode on multimeter to take the impedence on all the large inductors ...After that take some voltage measurments , and post them here .
post schematics and boardview

[SMDFlea]

Re: HP 15-F233 motherboard no power

@Lapfix ,the schematic and boardview https://www.badcaps.net/forum/showthread.php?t=84248

[Mo7babel]

Re: HP 15-F233 motherboard no power

@lapfix
all inductor are ok (multimeter indicate 0.00V)
the statements :

DC_JACK :
VDD = 19V
AD_ID = 0.47V
LED1 = LED2 =5.00V

INDUCTOR :
PL5 : 5VS5_5 = 5.1V
PL25 : 1.35VSUS_S = 0.00V
PL17 : VCORE = 0.00V
PL14 : 1.8VALW = 1.82V
PL15 : 1.05VS5 = 1.05V
PL9 : BQPHASE = 3.06V
PL7 : 3.3VS5 = 3.37V

[emestee]

Re: HP 15-F233 motherboard no power

You were suggested to test impedance to ground, but you are testing voltages. Do that first to exclude shorts on major rails.

When posting voltages, you need to say what state the machine was in.

Take a look at the charger IC (PU1) and its switches, see what's on its CMSRC and ACDET, and what it outputs on ACPRES. Nothing here will make sense until you know the 19v rail is reliably turned on.

[Mo7babel]

Re: HP 15-F233 motherboard no power

here are the measurements made in the DIODE position in one direction then in the other:
PL19: 2.2V, 0.3V
PL25: 0.3V, 0.2V
PL17: 0V, 0V !!!
PL14: 1V, 0.4V
PL15: 0.05V, 0.1V
PL16: 0.05V, 0.1V
PL7: 0.6V, 0.3V
PL9: 0L, 0.2

PU1:
ACDET = 2.7V, CMRC = 19V

the motherboard doesn't have a fan so i can't tell you its condition.
today I redid the measurements and all the voltage is at OV. when i press the power button, the voltages activate briefly and then return to 0.

*
you were right, there is a short circuit at PL17 but how do you know which component it is ?

[Mo7babel]

Re: HP 15-F233 motherboard no power

I just unsolder PL5 and the short circuit is on the VCORE line, there are a lot of caps on this line. I just hope it's not the CPU.

[emestee]

Re: HP 15-F233 motherboard no power

when i press the power button, the voltages activate briefly and then return to 0.

you were right, there is a short circuit at PL17 but how do you know which component it is ?

The short triggers protection. First, visually inspect all the components involved in VCORE voltage. If the CPU sits on a socket, remove it and see if the short goes away. Start measuring individual components for the short, refer to the schematics and boardview. Your #1 suspects would be the capacitors that connect to the ground or any other elements that do. If you can't find it, you can use a lab PSU to inject low voltage and limited current after the coil and see what warms up. You can remove the coil and try to start the board to see if it still goes into protection mode.

[piernov]

Re: HP 15-F233 motherboard no power

Short to ground must be reported with the exact value in resistance mode. CPU VCore is probably not shorted to ground.

[lapfix]

Re: HP 15-F233 motherboard no power

Idon't understand you when you say : measurements made in the DIODE position in one direction then in the other !!
For diode mode red probe on ground and with black probe you take the measurments .
so , take it again and post it .

PL25 (+1.35VSUS )what's the voltage before/after power on .

[Mo7babel]

Re: HP 15-F233 motherboard no power

@lapfix
I made the measurements by placing red to ground and then black to ground to see if the short circuit exists in both directions.
the red to the ground, are the first values that I have already given above.

on PL25 it is always at 0V whatever the poisition of the power button.

@emestee

I don't have an adjustable PSU so I use 5V, 200mA and it heats a little bit on the CPU.
the CPU is soldered.

[jijunmedia]

Re: HP 15-F233 motherboard no power

HP 15-3000NX (DAG7BLMB8D0)
new model 16mb bios needed
i atached old bios this problem is no display
caps led blink 5 long beep 3 short beep
please help me

[lapfix]

Re: HP 15-F233 motherboard no power

the measurements at Post n4 are not taken by diode mode ! they are the voltages measurements . there's no 2 direction too as you mention at post n10.

So until now ,we didn't know the impedance to ground on all coils .

[SMDFlea]

Re: HP 15-F233 motherboard no power

HP 15-3000NX (DAG7BLMB8D0)
new model 16mb bios needed
i atached old bios this problem is no display
caps led blink 5 long beep 3 short beep
please help me

Your bios request has been copied and moved to a new thread in the "Bios Requests" sub-forum .Thats where all bios request should go .

https://www.badcaps.net/forum/showthread.php?t=84298

[Mo7babel]

Re: HP 15-F233 motherboard no power

Iwas talking about post 6
PL19: 0.3
PL25: 0
PL17: 0
PL14: 0.4
PL15: 0
PL16: 0.1
PL7: 0.3V,
PL9: 0.3

these values are a little different than the previous ones because I have a little heat the CPU.
I now think that the short circuit is certainly on the soldering of the CPU or even the CPU which is failing. What do you think?

[emestee]

Re: HP 15-F233 motherboard no power

@lapfix
I made the measurements by placing red to ground and then black to ground to see if the short circuit exists in both directions.
the red to the ground, are the first values that I have already given above.

on PL25 it is always at 0V whatever the poisition of the power button.

@emestee

I don't have an adjustable PSU so I use 5V, 200mA and it heats a little bit on the CPU.
the CPU is soldered.

You fed 5V to CPU VCORE?

[Mo7babel]

Re: HP 15-F233 motherboard no power

No. there is neither + VCORE nor the other tensions. I think the CPU is burned out. it may be a cooling defect. the CPU does not have a fan. unfortunately I have no means to continue the repair. I think the adventure ends here and thank you to everyone who contributed.
I would come back with another motherboard !

[emestee]

Re: HP 15-F233 motherboard no power

No. there is neither + VCORE nor the other tensions. I think the CPU is burned out. it may be a cooling defect. the CPU does not have a fan. unfortunately I have no means to continue the repair. I think the adventure ends here and thank you to everyone who contributed.
I would come back with another motherboard !

My understanding of your previous post is that you attached a 5V power supply to the CPU VCORE when testing it. After that test you are now seeing shorts on other lines. If that is true, then you might have burned the CPU.