820-2850-A: battery not detected

**DrFalken** · 02-02-2022, 07:50 AM

Re: 820-2850-A: battery not detected

Removed U7000 and found this:

Pin15 (CHGR_BMON) = short to GND

I'll order and replace it...

**mon2** · 02-02-2022, 08:32 AM

Re: 820-2850-A: battery not detected

Is the short still present with U7000 off the logic board ?

**DrFalken** · 02-02-2022, 08:42 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

Is the short still present with U7000 off the logic board ?

No short circuit on the logic board on pad/pin 15.
Without U7000 now the laptop turns on ONLY with battery + charger while before it turned on with charger or battery + charger
Charger led is still solid green.

**DrFalken** · 02-08-2022, 06:14 AM

Re: 820-2850-A: battery not detected

Originally posted by DrFalken

No short circuit on the logic board on pad/pin 15.
Without U7000 now the laptop turns on ONLY with battery + charger while before it turned on with charger or battery + charger
Charger led is still solid green.

U7000 changed with a brand new one.

Actual voltages (without battery):
Pin01 (CHGR_AGATE) = 14,79V
Pin02 (PPCHGR_DCIN) = 16,4V
Pin03 (CHGR_ACIN) = 3,87V
Pin05 (CHGR_ICOMP) = 0,09V
Pin06 (CHGR_CELL) = 3,39V
Pin07 (CHGR_VCOMP) = 0V
Pin08 (CHGR_VNEG) = 0,03V
Pin09 (CHGR_AMON) = 0V
Pin10 (SMBUS_SMC_5_G3_SDA) = 3,34V
Pin11 (SMBUS_SMC_5_G3_SCL) = 3,34V
Pin12 (PP3V42_G3H) = 3,39V
Pin13 (CHGR_RST_L) = 3,39V
Pin14 (SMC_BC_ACOK) = 3,24V
Pin15 (CHGR_BMON) = not measured
Pin16 (CHGR_BGATE) = 0
Pin17 (CHGR_CSO_N) = 0,16V
Pin18 (CHGR_CSO_P ) = 0,16V
Pin19 (PP5V1_CHGR_VDD) = 1V drop to 0
Pin20 (PP5V1_CHGR_VDDP) = 1V drop to 0
Pin21 (CHGR_LGATE) = 0
Pin22 (GND) = 0
Pin23 (CHGR_PHASE) = 0,16V
Pin24 (CHGR_UGATE) = 0
Pin25 (CHGR_BOOT) = 0
Pin26 (CHGR_SGATE ) = not measured
Pin27 (CHGR_CSI_N) = 1,5V
Pin28 (CHGR_CSI_P ) = 1,48V

Charger led is solid green.
Laptop now is not turning on at all

Update: PPBUS_G3H = 0,16V and 167 Ohm to GND

**DrFalken** · 02-09-2022, 04:11 AM

Re: 820-2850-A: battery not detected

Other readings:

R7050 0 Ohm
R7051 12.6 Ohm (should be 2.2)
R7052 0 Ohm
C7050 1216 nF

**mon2** · 02-09-2022, 05:36 AM

Re: 820-2850-A: battery not detected

Few comments:

1) PP3V42_G3H is a low value. Remove all power. Meter in resistance mode. What is the resistance to ground for PP3V42_G3H ?

2) the current sense resistor values are critical. If wrong resistance then the wrong current will be sensed and will lead to shut down of u7000.

3) are you confident that u7000 was properly soldered? Use high heat, initially low air pressure but with some flux on top side of u7000. Go in circles on top of u7000. Allow the chip to melt and sink naturally. Careful to not blow off surrounding parts. If needed, increase the air pressure. Then while balls are melted, use a tweezer to gently nudge the u7000 chip. It should move but will bounce back, naturally. This corrects any solder ball shorts. Do this a few times and allow the board to cool.

Then check the current sense loop circuit again for u7000.

4) also post the resistance to ground for ppbus_g3h. No power, meter in resistance mode.

**DrFalken** · 02-09-2022, 08:56 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

Few comments:

1) PP3V42_G3H is a low value. Remove all power. Meter in resistance mode. What is the resistance to ground for PP3V42_G3H ?

2) the current sense resistor values are critical. If wrong resistance then the wrong current will be sensed and will lead to shut down of u7000.

3) are you confident that u7000 was properly soldered? Use high heat, initially low air pressure but with some flux on top side of u7000. Go in circles on top of u7000. Allow the chip to melt and sink naturally. Careful to not blow off surrounding parts. If needed, increase the air pressure. Then while balls are melted, use a tweezer to gently nudge the u7000 chip. It should move but will bounce back, naturally. This corrects any solder ball shorts. Do this a few times and allow the board to cool.

Then check the current sense loop circuit again for u7000.

4) also post the resistance to ground for ppbus_g3h. No power, meter in resistance mode.

Thank you for the help !

1) 176.6 KiloOhm
2) I've replaced R7051 with a 2.2 Ohm but no progress
3) In doubt I've removed it and replaced with a another brand new one, checked the solders but same issue
4) 171.8 Ohm

PP3V42_G3H stuck at 3.39V

**mon2** · 02-09-2022, 09:35 AM

Re: 820-2850-A: battery not detected

4) 171.8 Ohm

That is a low resistance for PPBUS_G3H.

Remove all power.

Remove fuse F7040 (for now). Then check the resistance to ground (2k scale is ok) on F7040, pin # 1 and then # 2 of the SMD pads.

Which side has the very low resistance ?

Is it the source (U7000 side) or the sink (pin # 2) ?

If pin # 2 is with the low resistance, power up without F7040 installed.

Then check the voltage on pin # 1 of the SMD pad -> now do you see a proper voltage for PPBUS_G3H ?

If not, leave this fuse OFF till we can get a proper voltage on PPBUS_G3H.

Measure PPDCIN_G3H.

Post your readings.

**DrFalken** · 02-09-2022, 10:07 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

That is a low resistance for PPBUS_G3H.

Remove all power.

Remove fuse F7040 (for now). Then check the resistance to ground (2k scale is ok) on F7040, pin # 1 and then # 2 of the SMD pads.

Which side has the very low resistance ?

Is it the source (U7000 side) or the sink (pin # 2) ?

If pin # 2 is with the low resistance, power up without F7040 installed.

Then check the voltage on pin # 1 of the SMD pad -> now do you see a proper voltage for PPBUS_G3H ?

If not, leave this fuse OFF till we can get a proper voltage on PPBUS_G3H.

Measure PPDCIN_G3H.

Post your readings.

F7040 removed:
PIN1 = 169 Ohm
PIN2 = 1.88 MegaOhm
PPDCIN_G3H (on Q7080 PIN8) = 16.29V - 16.48V

**mon2** · 02-09-2022, 10:20 AM

Re: 820-2850-A: battery not detected

So the fault is in the source side = U7000 circuit. The input voltage to U7000 is good.

Perhaps one of the caps are damaged / shorted.

See attached.

Start with removing (just for now), the current sense resistors @ R7051 - remove only this one and then check if the resistance has changed on this line. Do not lose the resistor.

If no improvement on the resistance, proceed to remove the resistor @ R7052. Measure again. Do not lose the resistor.

Any improvement on the resistance ?

If you remove one leg of L7030 then you can create an isolated island of parts to narrow down which cluster of parts has the fault. However, L7030 will be with heavy solder and copper plane. Proceed to lift one leg but only if you feel comfortable.

Alternatively, as a guess, perhaps the fault is in one of the highlighted caps.

Consider to lift one leg of the 22uf @ C7040. Once the one leg is lifted, check the resistance to ground again on pad # 1 of fuse F7040.

Do not power up with these parts removed till the root cause can be fixed.

Attached Files

**DrFalken** · 02-09-2022, 10:53 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

So the fault is in the source side = U7000 circuit. The input voltage to U7000 is good.

Perhaps one of the caps are damaged / shorted.

See attached.

Start with removing (just for now), the current sense resistors @ R7051 - remove only this one and then check if the resistance has changed on this line. Do not lose the resistor.

If no improvement on the resistance, proceed to remove the resistor @ R7052. Measure again. Do not lose the resistor.

Any improvement on the resistance ?

If you remove one leg of L7030 then you can create an isolated island of parts to narrow down which cluster of parts has the fault. However, L7030 will be with heavy solder and copper plane. Proceed to lift one leg but only if you feel comfortable.

Alternatively, as a guess, perhaps the fault is in one of the highlighted caps.

Consider to lift one leg of the 22uf @ C7040. Once the one leg is lifted, check the resistance to ground again on pad # 1 of fuse F7040.

Do not power up with these parts removed till the root cause can be fixed.

R7051 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm
R7052 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm
L7030 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...
C7040 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...

C7040 = 23.17 uF

**mon2** · 02-09-2022, 11:16 AM

Re: 820-2850-A: battery not detected

R7051 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm

This part can be put back.

R7052 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm

This part can be put back.

L7030 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...

So this means that the bad cap is upstream and on the pin # 1 side of the removed L7030.

C7040 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...

This part can be put back.

Leave the inductor @ L7030 off the logic board for now.

a) What is the resistance to ground for L7030, pin # 1 ?

b) What is the resistance to ground for C7030 ?

You may have a shorted mosfet. Can check this next.

**DrFalken** · 02-09-2022, 11:20 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

R7051 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm

This part can be put back.

R7052 removed, resistance to GND on F7040 pad 1 = 168.8 Ohm

This part can be put back.

L7030 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...

So this means that the bad cap is upstream and on the pin # 1 side of the removed L7030.

C7040 removed completely, resistance to GND on F7040 pad 1 = over 200 MegaOhm...

This part can be put back.

Leave the inductor @ L7030 off the logic board for now.

a) What is the resistance to ground for L7030, pin # 1 ?

b) What is the resistance to ground for C7030 ?

You may have a shorted mosfet. Can check this next.

Before I put back R7051, R7052 & C7040:
- resistance to ground for L7030, pin # 1 = 171.8 Ohm

I'm gonna put back R7051, R7052 & C7040 and update soon.

**mon2** · 02-09-2022, 11:23 AM

Re: 820-2850-A: battery not detected

Ok. This confirms the short is to the left side of the schematic of U7000. That is, to the LEFT of L7030.

Still leave off L7030 till the root cause can be located. The other parts can be placed back on since they are innocent. If you do find that pin # 2 pad of L7030 sinks on the resistance then there is a fault on this group of parts but sounds like the fault is upstream.

**DrFalken** · 02-09-2022, 11:49 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

Ok. This confirms the short is to the left side of the schematic of U7000. That is, to the LEFT of L7030.

Still leave off L7030 till the root cause can be located. The other parts can be placed back on since they are innocent. If you do find that pin # 2 pad of L7030 sinks on the resistance then there is a fault on this group of parts but sounds like the fault is upstream.

Put back R7051, R7052 & C7040:
L7030 pad 1 = 170 Ohm
L7030 pad 2 >20 MegaOhm
C7030 pin 1 >20 MegaOhm

**mon2** · 02-09-2022, 11:59 AM

Re: 820-2850-A: battery not detected

Ok. Post the resistance to ground for C7030.

Mosfet Q7035 may be shorted.

After the above resistance check, do the follow (resistance checks are always with the power removed)

Measure & post:

resistance between SOURCE (1-2-3) & DRAIN (5-6-7-8) of Q7035

resistance between SOURCE (1-2-3) & GATE (4) of Q7035

resistance between GATE (4) & DRAIN (5-6-7-8) of Q7035

Post each reading.

**DrFalken** · 02-09-2022, 12:07 PM

Re: 820-2850-A: battery not detected

Originally posted by mon2

Ok. Post the resistance to ground for C7030.

Mosfet Q7035 may be shorted.

After the above resistance check, do the follow (resistance checks are always with the power removed)

Measure & post:

resistance between SOURCE (1-2-3) & DRAIN (5-6-7-8) of Q7035

resistance between SOURCE (1-2-3) & GATE (4) of Q7035

resistance between GATE (4) & DRAIN (5-6-7-8) of Q7035

Post each reading.

Q7035 left on board:
resistance between SOURCE (1-2-3) & DRAIN (5-6-7-8) of Q7035 = 171.3 Ohm
resistance between SOURCE (1-2-3) & GATE (4) of Q7035 = 46.9 Ohm
resistance between GATE (4) & DRAIN (5-6-7-8) of Q7035 = 220 Ohm

Sorry but I've to leave but will back tomorrow: if You have anything else to check, please post and I'll report tomorrow
Thank you very much for your guide !

**mon2** · 02-09-2022, 02:15 PM

Re: 820-2850-A: battery not detected

Remove Q7035 from the logic board.

Then check the resistance to ground of L7030, pin # 1 pad again.

If the resistance improves and is no longer low, proceed to:

a) check the resistance across the same combination of pins on the removed Q7035 mosfet. Likely the low resistance values will show while the part is no longer on the logic board.

b) check the resistance to ground of the PCB pads where Q7035 was soldered to confirm that U7000 is not to blame. If there are low resistance readings with Q7035 off, post the values and can troubleshoot further.

Suspecting that Q7035 is defective and needs to be replaced.

**DrFalken** · 02-10-2022, 03:07 AM

Re: 820-2850-A: battery not detected

Originally posted by mon2

Remove Q7035 from the logic board.

Then check the resistance to ground of L7030, pin # 1 pad again.

Q7035 removed:
L7030 pad #1 > 20 MegaOhm

Originally posted by mon2

If the resistance improves and is no longer low, proceed to:

a) check the resistance across the same combination of pins on the removed Q7035 mosfet. Likely the low resistance values will show while the part is no longer on the logic board.

Q7035 readings:
resistance between SOURCE (1-2-3) & DRAIN (5-6-7-8) of Q7035 = 174.3 Ohm
resistance between SOURCE (1-2-3) & GATE (4) of Q7035 = 49.6 Ohm
resistance between GATE (4) & DRAIN (5-6-7-8) of Q7035 = 220 Ohm

Originally posted by mon2

b) check the resistance to ground of the PCB pads where Q7035 was soldered to confirm that U7000 is not to blame. If there are low resistance readings with Q7035 off, post the values and can troubleshoot further.

Suspecting that Q7035 is defective and needs to be replaced.

Resistance of PAD 1-2-3 to GND = GND
Resistance of PAD 4 to GND > 20 MegaOhm
Resistance of PAD 5-6-7-8 to GND > 20 MegaOhm

820-2850-A: battery not detected

820-2850-A: battery not detected

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