P3V3A has low resistance

[kalilinux25]

Unit has no power , Ive check the 5V and 3v line , the 3v line has low resistance showing 300ohms, then I tried to isolate the issue and foudn out the P3V3A has issue and tried pump voltage 1v pch gets warm. After removing the possible pch problem still having low resistance on the P3V3A.

I already remove the RAM ,PROCESSOR, DC JACK, jsut to Isolate

but what is the most best option to do on troubleshooting this?


hope somoene has insight

HP 1000 G4-2000 CQ35 KF14CHR-6050A2493101-MB-A01-002

[Mod. Edit-Vesko356] Schematic ---> https://www.badcaps.net/forum/showth...633#post409633
Boardview ---> https://www.badcaps.net/forum/showth...96#post1261396

Reminder: rules and organization of this section
https://www.badcaps.net/forum/showthread.php?t=117483

[mon2]

Re: P3V3A has low resistance

1) the schematic should only be posted in the schematic forum

2) can you clarify where you are measuring this low resistance? Use only the exact netnames from the shared schematic. Is it the switching power rail or the LDO rail?

Suspecting VRP3V3A at U6100 ? If yes, with care, flux and lift one leg of L6100 inductor. Do not power up. Check the resistance to ground on each side of L6100 pcb pads. Which side is with the low resistance? Producer side = U6100 or consumer side = downstream?

[kalilinux25]

Re: P3V3A has low resistance

1) the schematic should only be posted in the schematic forum

2) can you clarify where you are measuring this low resistance? Use only the exact netnames from the shared schematic. Is it the switching power rail or the LDO rail?

Suspecting VRP3V3A at U6100 ? If yes, with care, flux and lift one leg of L6100 inductor. Do not power up. Check the resistance to ground on each side of L6100 pcb pads. Which side is with the low resistance? Producer side = U6100 or consumer side = downstream?

ok noted-

PAD6100 pin 2 has the 100 ohms ressitance , If I try pumping vokltage just taking 2.8v 10miliamps very low to produce heat. VRP3V3A

due i dont have a theremal camera I cant find what is causing its low resistance, the board state I remove the pch and bios chip just to Isolate teh short, but still no luck

[mon2]

Re: P3V3A has low resistance

At 10mA current draw, there is no short here.

With no power faults, start with the charger IC and the usual DCin mosfets.

With care, measure the voltage to ground of each pin of U6000. Post each measurement.

Need to confirm the ACDRV, REGN, VCC, etc. are ok for the charger IC. Be sure the AC adapter is the proper one for this laptop.

From the original post, are these always on rails not working? Input voltage rails are ok?

[kalilinux25]

Re: P3V3A has low resistance

At 10mA current draw, there is no short here.

With no power faults, start with the charger IC and the usual DCin mosfets.

With care, measure the voltage to ground of each pin of U6000. Post each measurement.

Need to confirm the ACDRV, REGN, VCC, etc. are ok for the charger IC. Be sure the AC adapter is the proper one for this laptop.

From the original post, are these always on rails not working? Input voltage rails are ok?

should I solder back the bios chip and pch?
or its fine withoud conencting the PAD6100?
I was reading 100ohms in the VRP3V3A line

[Udemzy]

Re: P3V3A has low resistance

You remove the possible pch problem or you removed the pch chip from the board?

[mcplslg123]

Re: P3V3A has low resistance

Hold on friends, I just fixed a dead mb with same part number yesterday. The resistance to GND on 3V Coil is 102 Ohms-so nothing is wrong here. My board after fixing is booting to windows desktop and i confirm this resistance is the norm on 3V coil on this MB.

[kalilinux25]

Re: P3V3A has low resistance

Hold on friends, I just fixed a dead mb with same part number yesterday. The resistance to GND on 3V Coil is 102 Ohms-so nothing is wrong here. My board after fixing is booting to windows desktop and i confirm this resistance is the norm on 3V coil on this MB.

shoot i think i messud up, I thinks I should connect it again the pch and everything, but how those it work if it has low resitance?

[Sephir0th]

Re: P3V3A has low resistance

It is a actually hard to believe that this resistance to GND is a healthy value on this board, but If someone reputable as mcplslg123 shares this, it must be true...

A rare case, well done.

[mon2]

Re: P3V3A has low resistance

I recall a reference design from a semiconductor firm (Moschip) who had a 120 ohm resistor at the output of a LDO. Asked them why would they do this and their engineering manager replied that it is for a quick discharge of the power rail when the unit is turned off. Perhaps the same case here, for a discharge / bleed of the power rail.

[mcplslg123]

Re: P3V3A has low resistance

I stand by by comments on post#7 as i re-checked the measurement today and its 102 Ohms on 3V coil.However,on 5V coil its in Kohms range. Indeed bit strange design. I too was tempted too beleive there is some short on 3V rail but perhaps experience didnt take me to a rabbit hole.

[kalilinux25]

Re: P3V3A has low resistance

I stand by by comments on post#7 as i re-checked the measurement today and its 102 Ohms on 3V coil.However,on 5V coil its in Kohms range. Indeed bit strange design. I too was tempted too beleive there is some short on 3V rail but perhaps experience didnt take me to a rabbit hole.

i jsut managed to buy a new pch and replace it with new one, hope I propely installed the pch back ,Ill post all the readings of the laptop hope somoen can guide me

[kalilinux25]

Re: P3V3A has low resistance

I solder back a new pch in this is readign of coil
U600 READING
TI_BQ24728_QFN_20P
1. ACN= 19.5
2. ACP= 19.5
3. CMSRC = 19.5
4. ACDRV = 25.31
5. ACPRES = 2.9V
6. ACDET = 2.6
7. IOUT = 0V
8. SDA = 3.3V
9. SCL = 3.3V
10. ILIM = 0V
11. BATDRV = 2.5V
12. SRN = 2.5V
13. SRP = 2.5V
14. GND = 0V
15. LODRV = 0V
16. REGN = 6.0v
17. BTST = 5.9v
18. HIDRV = 2.5v
19. PHASE = 2.5v
20. VCC = 18.8v




coils
(resistance to ground)
no cmos battery and ram plugged in
L6710 =15ohms
L6610 =10ohms
L6620 =10ohms
L6500 = 26ohms
l6300 = 20hms
L6200 = 493 ohms
C6100 = 100ohms
L6100 =20k
L6000 = 3megaohms

[mcplslg123]

Re: P3V3A has low resistance

I think you took measurement of coils with cpu in socket. If yes, then resistance seems normal. Wiser to take cpu out and measure resistance again. You should get resistance to GND on vcore/gfx in Kohms range. Confirm it.

Going by your measurements of charging IC, i beleive the dc jack light is not glowing as ACOK aka ACPRES is pulled a little low at 2.9V-must be 3.3V. R6024,pin1 is 3.3V? If 3.3V is available as pull up and still its showing 2.9V on ACOK-that indicates a problem.In my experience this is related to EC Firmware. Suggest to check EC BIOS and its connectivity to various resistors as per schematic.

PS: I wont solder a new PCh before getting atleast the dc jack light glowing.

[kalilinux25]

Re: P3V3A has low resistance

I think you took measurement of coils with cpu in socket. If yes, then resistance seems normal. Wiser to take cpu out and measure resistance again. You should get resistance to GND on vcore/gfx in Kohms range. Confirm it.

Going by your measurements of charging IC, i beleive the dc jack light is not glowing as ACOK aka ACPRES is pulled a little low at 2.9V-must be 3.3V. R6024,pin1 is 3.3V? If 3.3V is available as pull up and still its showing 2.9V on ACOK-that indicates a problem.In my experience this is related to EC Firmware. Suggest to check EC BIOS and its connectivity to various resistors as per schematic.

PS: I wont solder a new PCh before getting atleast the dc jack light glowing.

you mean that Its fine to check voltages without pch is connected?

[kalilinux25]

Re: P3V3A has low resistance

I think you took measurement of coils with cpu in socket. If yes, then resistance seems normal. Wiser to take cpu out and measure resistance again. You should get resistance to GND on vcore/gfx in Kohms range. Confirm it.

Going by your measurements of charging IC, i beleive the dc jack light is not glowing as ACOK aka ACPRES is pulled a little low at 2.9V-must be 3.3V. R6024,pin1 is 3.3V? If 3.3V is available as pull up and still its showing 2.9V on ACOK-that indicates a problem.In my experience this is related to EC Firmware. Suggest to check EC BIOS and its connectivity to various resistors as per schematic.

PS: I wont solder a new PCh before getting atleast the dc jack light glowing.

L6300 = 31ohms = VRP1V05S_VCCP
l6620 = 3K = PVCORE
L6610 = 3K = PVCORE
L6500 = 4K = VRPVSA
L6710 = 10K =

[mcplslg123]

Re: P3V3A has low resistance

Yes, you can apply power on mb without PCH/SIO for test purpose.
You have not confirmed whether dc jack light is glowing or not?

[kalilinux25]

Re: P3V3A has low resistance

Yes, you can apply power on mb without PCH/SIO for test purpose.
You have not confirmed whether dc jack light is glowing or not?

Still no light
VRP1V05S_VCCP is this normal? to have low resistance?

[kalilinux25]

Re: P3V3A has low resistance

Still no light
VRP1V05S_VCCP is this normal? to have low resistance?

update 3V AND 5V ic is a liitle bit warm
U6100 -BQ24728

[mcplslg123]

Re: P3V3A has low resistance

Still no light
VRP1V05S_VCCP is this normal? to have low resistance?

Yes, Resistance is normal. This is for PCH power rail-so will have low resistance.