A1990 that will not charge battery

[mon2]

Hi. Have a student's macbook A1990 unit with slight liquid damage. Removed and cleaned the motherboard.

The logic board is now powering up to the desktop. Very pleased.

But the battery will not charge and stuck @ 1% all day.

Checked the battery - it is dead @ 0 volts. The power rail for the charger circuit was at 0 volts.

Traced it back to UB740 which is an AND gate and should be '1' @ output to turn ON the battery charger IC # UB700.

Pin 2 of this SOT323 AND gate remains LOW - why??

See that CD3215C USB C @ UB400 (pin G10) is OR'ed with CD3215C USB C @ UB300 and also has a common 100k pull-down resistor.

The resistor is fine @ 90k or so to ground.

Any ideas on what could be wrong?

Have removed the SOT323 AND gate but pin # 2 of this logic AND gate remains LOW. Tested with BOTH USB C ports.

Could BOTH UB300 & UB400 be defective?

If yes, need to order 2 of these devices asap. The macbook powers up just fine and 20V is negotiated.

I suppose that we could force UB700 (battery charger IC) to be always ON with a logic high but perhaps a plan 'C' if we do not get this to work properly.

My mind is drifting but could the CD3215 behave badly due to no I2C communication with the I2C bus master? Not clear on how the CD3215 plays the role for the battery charger. We do have an I2C bus analyzer but will consume time to debug at that level...

Please help - need to get this student operational asap. Thanks.

OMG - there is an identical clone of the 2 x CD3215 + another single gate AND on the other side...will investigate that leg.

[SMDFlea]

Re: A1990 that will not charge battery

Have you checked RB232

[mon2]

Re: A1990 that will not charge battery

hi. thanks for your reply. Yes, RB232 is @ 90k or so.

Just tested the other 2 x CD3215 and local single gate AND - same exact operation.

The output of the AND gate remains low. The local resistor (pull-down) is @ R3032 which is also checking out to be fine.

Pin 2 of this clone on the other side of the PCB remains also LOW.

Would you know if the CD3215 can auto-enable the use of the battery charger? That is, is the GPIO6 pin that appears to be used on the CD3215 goes HIGH automatically or is instructed to do so from an upstream controller (master)?

The plot thickens...

[mon2]

Re: A1990 that will not charge battery

I may be thinking down the wrong path here...

a) have the battery REMOVED from the logic board

b) the honker pads for the battery interface are pulsing @ 1Hz or a bit slower @ 12v / 0v and repeating. I think this is a good sign?

c) what is the function of the AND gate? To turn on the local 5v

PP5V_S4_X_USBC created by U3500 (remains OFF?)

or

PP5V_S4_T_USBC UB700 (remains OFF?)

When should the above rails turn ON? What are they used for?

[SMDFlea]

Re: A1990 that will not charge battery

UPC_T_5V_EN goes to UPC_T_5V_EN_R to UB700, it enables the lower gate for QB701 , thats as far as i can tell anyway. How the CD3215 GPIO6 pin is powered ive no idea.

[MobileXT]

Re: A1990 that will not charge battery

Hi. Have a student's macbook A1990 unit with slight liquid damage. Removed and cleaned the motherboard.

The logic board is now powering up to the desktop. Very pleased.

But the battery will not charge and stuck @ 1% all day.

Checked the battery - it is dead @ 0 volts. The power rail for the charger circuit was at 0 volts.

Traced it back to UB740 which is an AND gate and should be '1' @ output to turn ON the battery charger IC # UB700.

Pin 2 of this SOT323 AND gate remains LOW - why??

See that CD3215C USB C @ UB400 (pin G10) is OR'ed with CD3215C USB C @ UB300 and also has a common 100k pull-down resistor.

The resistor is fine @ 90k or so to ground.

Any ideas on what could be wrong?

Have removed the SOT323 AND gate but pin # 2 of this logic AND gate remains LOW. Tested with BOTH USB C ports.

Could BOTH UB300 & UB400 be defective?

If yes, need to order 2 of these devices asap. The macbook powers up just fine and 20V is negotiated.

I suppose that we could force UB700 (battery charger IC) to be always ON with a logic high but perhaps a plan 'C' if we do not get this to work properly.

My mind is drifting but could the CD3215 behave badly due to no I2C communication with the I2C bus master? Not clear on how the CD3215 plays the role for the battery charger. We do have an I2C bus analyzer but will consume time to debug at that level...

Please help - need to get this student operational asap. Thanks.

OMG - there is an identical clone of the 2 x CD3215 + another single gate AND on the other side...will investigate that leg.

It could be the ISL9239 OR ISL9240 is bad. This chip is responsible for the battery charging.

[mon2]

Re: A1990 that will not charge battery

hi. I think that I am chasing a ghost. that is, there is nothing wrong with the battery charging leg of the design. The mating battery pads are oscillating @ 12vxx / 0 volts since we have removed the battery.

One of our techs believes that at least one of the battery pouches appears a bit puffy. Perhaps this A1990 (that is not very old) has a dead battery?

Any ideas on how to validate this conclusion? Unless we are not searching with the proper keywords, there appears to be little in available tools on Aliexpress to allow for external charging of the same battery (ie. without our logic board).

We do see the BMS board with the battery and perhaps some liquid damage took out this unit? The lightning bolt symbol does appear on the desktop but after attempting to charge all day, remained @ 1%.

On the missing 5 volt rail that we have been chasing, according to the closest datasheet to the CD3215 and thanks to wikipedia post - please see attached graphic.

We DO HAVE 20V = PP_HV which must be powering VBUS. Respectively if PP_HV is ON, PP_5V0 will be OFF. This makes perfect sense.

As noted, we have tested each CD3215 controller and all 4 are behaving the same way. Since we have a 12vxx on the battery contacts, the ISL9240 is working fine.

Welcome any comments / corrections on our final answer

Will put this back together and ask if the client wants to purchase a fresh battery which looks $$. Works fine with the adapter.

[piernov]

Re: A1990 that will not charge battery

https://www.badcaps.net/forum/showthread.php?t=90356

2.2. Battery not charging

First thing is to try another battery. Then try another battery. Finally try another battery. 99% of battery problems are the battery itself

[mon2]

Re: A1990 that will not charge battery

lol

Funny in hindsight. Have a confirmed known-good battery for this A1990 in transit for Monday.

Crossing our fingers. Thanks again Piernov!

PS: Did see corrosion on the battery flex cable which is about a 5 conductor on the BMS area. Attempted to clean as much as possible but strong possibility that this cable is gone too long with the liquid damage. Have a fresh cable incoming with the replacement battery as well.

[mon2]

Re: A1990 that will not charge battery

@piernov, you were right, as always. The new battery arrived today as well as the new BMS flex cable.

First, attempted to replace the BMS cable and we had observed some liquid damage on the mating ffc cable connectors and cable pads. Did our best to clean this up but the battery remained @ 1% charge all day.

One of the battery pouches appeared to be physically thicker than others. Replaced the battery with the new one from today.

Immediately the battery meter responded with a 71% charge -> been charging for the last bit and is upto 84% and climbing. The macbook is able to operate on the battery alone as well.

All good. Many thanks for the advice.