Lenovo ideapad 5 windows 11 update disable charging circuit?

[bogart219]

Which side?

The bottom side

[m1ch43lzm]

Edit: please post a picture of the area around both inductors
One side of the inductors should have continuity to the fuses, the other side won't
Measure resistance to GND at the fuses

[bogart219]

Edit: please post a picture of the area around both inductors
One side of the inductors should have continuity to the fuses, the other side won't
Measure resistance to GND at the fuses

Here you go!



Top side of both inductor pads have continuity to the two fuses, the other side don't, like you indicated.
Question, in my resaerch, a guy on UT said that coils (inductors) are always connected to the positive rail only, is this an accurate statement?

[m1ch43lzm]

The short could be in the cap marked in red PC8309, or any other cap near the BQ on the other side of the board
To double check, measure resistance across PC8309 if you still have 43ohm

In yellow i marked what appears to be some stray solder? Inspect the board for stray solder blobs

You haven't posted the resistance measurements, you may edit the picture with the measurements written on it

If you're confortable with voltage injection, set your bench PSU to 1v (don't go higher, double check with multimeter) and solder a wire to the bottom of PL8301-PL8302, connect that to the + of the bench PSU
The GND you can connect to a screw hole
Take note of the current draw, check with the thermal camera which component gets hot, may be a cap near the BQ, PC8309 or PC8307 near the audio IC (unlikely)

[bogart219]

Yes still have 46 ohms across PC8309. Took care of the solder gob. Could you please tel me again what resistance measurements you want?
Due to space constraints, I'm doing this smd work, not on my work bench but on a table next to my computer. My bench PSU is on my bench, I will have to make room and move my camera over there. I'll get back to you, Thanks!

[m1ch43lzm]

Yes still have 46 ohms across PC8309

So the short is on the input of the BQ charger, could be anything from a cap, to the BQ itself
Normal resistance should be several Kohms or higher (maybe unstable value as there are caps in parallel, thats ok)



OK, please post resistance measurements:

- Across CU206 (+5VALW), should be very high on Kohms - Mohms
- From PF8302 to GND (TBT_VSYS), now it should be very high in Kohms or more

[bogart219]

Hello, I just did those test with soldering wires to the bottom of PC8301 & PC8302. was pulling between 200 & 300 at .9 volts. this cap in the picture was glowing. and looks discolored. I believe its PC5302 going by board view.
NO Glowing on the BQ chip, PC8309 or PC8307 The cap in the pic Glowing like a bitch.
CU206 to ground = .2 ohms across the cap = 14.2 ohms !
PF802 to ground = O/L

[m1ch43lzm]

I can't see the picture (maybe the forum ate it?), but you can remove PC5302 and the short should be gone

Is this one?


Unless its one of the caps on the other side of the board

But the low resistance on +5VALW worries me (14ohm), could be anything on the board, a cap, the TPS65994 or anything

[bogart219]

I can't see the picture (maybe the forum ate it?), but you can remove PC5302 and the short should be gone

Is this one?


Unless its one of the caps on the other side of the board

But the low resistance on +5VALW worries me (14ohm), could be anything on the board, a cap, the TPS65994 or anything

Sorry about that, that png must of been to big, here is a jpeg:



Is that a different boardview you use, its colorful not black and white?

[bogart219]

Brother, I got to leave the house and go and baby sit my grand kids.Thanks for all your help and knowledge. We can take this up tomorrow if you don't mind. Have a good evening

[m1ch43lzm]

Is that a different boardview you use, its colorful not black and white?

The software i used is FlexBV free edition by inflex aka Paul Daniels (@pldaniels on YT), he repairs mostly Apple laptops, sometimes other brands on his livestreams
https://www.badcaps.net/forum/troubl...acos-and-linux

Brother, I got to leave the house and go and baby sit my grand kids.Thanks for all your help and knowledge. We can take this up tomorrow if you don't mind. Have a good evening

Take care, have a good day too

[bogart219]

Good morning. I'm going to remove PC5302 and see what happens. The two mosfets and two inductors are still out of the board.

Just a quick recap, this lappy would not turn on or charge the battery. I replaced the power adapter and the battery., still nothing. The lappy did work with the battery hooked up but not just the adapter. The adapter would not charge the battery. I was able to charge the battery from my bench top PS.
The usb test meter showed 5 volts and no amps. Was getting 5 volts to two mosfets but the resistance readings of the those two looked screwy. Replaced the two mosfets with new ones, which I had a hard time doing. (new to this smd rework).
After replacing the fets, retested. Usb tester shows 5 volts but now at 6 to 700milliamps. removed the two fets I replaced and it still showed 6 to 7 hundred ma. Removed two inductors, the same.
Appears the TPS chips + terminals read to ground. It must be something I did when removing those fets, I'm assuming I mucked something up, or did I. I put Kaption tape all around those fets and used flux but something changed. I'm lost at this point.
I did a voltage injection of 1 volt pulling 2-300 ma. Found a cap near the BQ chip on the other side of the board glowing. (thermal camera). Will remove and see what happens.

[bogart219]

Removed PC5302. The short is still there, 5 volts 650 milliamps, F**K.
Removed PC8309 no difference.

After removal of the top two caps, voltage injection no longer produces any current at 1 volt.
TPS charge controller still red hot

[m1ch43lzm]

There's no way for the 5V from the charger to go to the system and draw 650mA, as the inductors and MOSFETs are removed from the board

VBUS_TBTA/VBUS_TBTB go straight from the USB-C ports to the TPS65994, and some other components, and that's the only IC with connections both to +5VALW and the USB-C ports

Suspect a dead TPS65994 as you still have a short on +5VALW of 14ohm, I told you that's not normal, that line should read from tens of Kohm upwards

Do not apply power to the board until that is fixed (5VALW showing a healthy resistance) and the TPS65994 is replaced along with the MOSFETs and inductors, I should have told you that, sorry

The shorted cap near the BQ was another issue, probably related to the original fault, as that's on the input of the BQ, in your laptop the BQ generates the main power rail, and charges the battery

[bogart219]

There's no way for the 5V from the charger to go to the system and draw 650mA, as the inductors and MOSFETs are removed from the board

VBUS_TBTA/VBUS_TBTB go straight from the USB-C ports to the TPS65994, and some other components, and that's the only IC with connections both to +5VALW and the USB-C ports

Suspect a dead TPS65994 as you still have a short on +5VALW of 14ohm, I told you that's not normal, that line should read from tens of Kohm upwards

Do not apply power to the board until that is fixed (5VALW showing a healthy resistance) and the TPS65994 is replaced along with the MOSFETs and inductors, I should have told you that, sorry

The shorted cap near the BQ was another issue, probably related to the original fault, as that's on the input of the BQ, in your laptop the BQ generates the main power rail, and charges the battery

Wow,some of what you said I don't quite understand. I bought that TPS65994 chip when I got the mosfets. Does this chip need reprogramed? If not I will hopefully replace the TPS65994 and put back the two mosfets and two inductors and then see if my short went away. I'll address those two caps after that.Thanks.

[bogart219]

Man, my confidence is getting low using this hot air gun taking off some of these components. I'm feeling like I bit off more than i can chew. Those last two caps I removed, I used 420 degree heat at 50% and it seemed like it took for ever. I used flux and put aluminum tape (seen a guy on YT suggest using that, I have a couple rolls from my HVAC days), around them instead of Kaption tape. Maybe that aluminum is sucking all the heat?, I don't know. I will proceed with caution. Very disappointed in my smd skills

[m1ch43lzm]

I'm not 100% sure if the TPS65994 needs to be programmed, or if it can be programmed by the motherboard when it powers on

Practice first on a dead board, this chip has a large GND pad on the underside, may require more heat, about 430-450 C I think, you don't want to rip the pads on the board
Afterwards tin the pads with 63/37 solder+flux

TI forums suggest that the chip has an internal ROM and they "spin" a new revision when the USB spec gets updated, and datasheet suggests that it communicates with the EC and the thunderbolt controller

I think it can program itself, if anybody has experience replacing TPS65994 please come in here
I have to go out, I won't be able to reply until late afternoon

[bogart219]

I'm not 100% sure if the TPS65994 needs to be programmed, or if it can be programmed by the motherboard when it powers on

Practice first on a dead board, this chip has a large GND pad on the underside, may require more heat, about 430-450 C I think, you don't want to rip the pads on the board
Afterwards tin the pads with 63/37 solder+flux

TI forums suggest that the chip has an internal ROM and they "spin" a new revision when the USB spec gets updated, and datasheet suggests that it communicates with the EC and the thunderbolt controller

I think it can program itself, if anybody has experience replacing TPS65994 please come in here
I have to go out, I won't be able to reply until late afternoon

Yeah ok friend, have a good afternoon!

[SMDFlea]

I'm not 100% sure if the TPS65994 needs to be programmed, or if it can be programmed by the motherboard when it powers on

The firmware is stored on an external 1MB chip.

https://www.badcaps.net/forum/troubl...65994ae-eeprom
https://www.badcaps.net/forum/troubl...are-request

[bogart219]

The firmware is stored on an external 1MB chip.

https://www.badcaps.net/forum/troubl...65994ae-eeprom
https://www.badcaps.net/forum/troubl...are-request

Hello, a few questions if you please. 1) Is this external chip something I can get? 2) How do I write it to my new TPS chip? 3) This is not a bios file correct, totally different correct? 4) where do I go to get this eeprom or chip? thank you very much1