820-00850 2019 MacBook Pro 13" Touch Bar (A1989) mysterious battery drain

[gboone]

Hi, I was given this laptop by my uncle who said:

• It would occasionally shutdown if not plugged in
• battery had been replaced
• touchbar would "strobe"

I disconnected touch bar components and strobing and sudden shutdowns were fixed. Recent updates were installed to the OS.

After fully charging the battery, with bluetooth disabled, no LAN cable and only wifi enabled, the laptop stayed on (screen on) for about 6-8 hours. Allowing screen to turn off while not in use, and it went for over a day.

BUT

When powered off, it would at some point have a drained battery. I tested for weeks:

• I disabled start up from lid opening
• powering it on, checking that yes it was still at 100%
• then I would turn it off
• I tried with lid up, and lid down - no difference - at some point it would no longer have any battery voltage

So I started looking at components with the back off:

• battery measured 0.01v
• 3 of 4 USB ports only showed 5v on USB meter - so no battery charging. The two on the right were both this way.
• However, one of the USB ports on the left showed 20v and the battery started to charge, drew current up to 1.8-2A
• pin 2 of L7030 showed 12.5v and pin 1 showed 2.8v fluctuating - I thought this was wierd
• I checked Q7030 and 40 - not shorted
• Once charged to 100% (says 100% on screen when lid opened), the USB ampmeter is showing 530ma of current at 19.9v or 20.2v, and all 4 USB ports are showing 20v
• I couldn't find any shorts, but R7063 (10k) is bad, it goes to U7000 CHGR_VBAT from PPVBAT_G3H_CONN

With battery connected, USB power disconnected, PP3V3_G3H is showing stable 3.4v and L7600 PP5V_G3S is showing stable 5.1v

With battery disconnected, USB power connected, everything seems fine but it's taking about 30-40ma. I couldn't find anywhere if this is normal, so not sure if this is something?

Other than the battery draining while off, it seems fine. Looking for ideas of what to check next, thanks!

[mon2]

Test with another known good battery. Try Mobile Sentrix (USA).

[gboone]

Test with another known good battery. Try Mobile Sentrix (USA).

Thank you for the tip!

[reformatt]

I will add that MAC's act erratically without the touchbar working as it messes with going into and out of sleep. I have seen some MAC's run fine when it's only the display side of the Touchbar malfunctioning and the touch side is working. Customers opt to leave as is as they don't use it.

Not sure if it's related to the fault, however it's something I'd be ruling out. A1989 touchbars aren't too expensive to buy.

[gboone]

That is very interesting, because it sure does seem that at some point the state of everything changes but I have no idea what from.

I didn't really get into testing the board until after disconnecting the touchbar. I tested the touch (top layer digitizer?) was working, but the display (bottom layer screen and backlight?) was glitchy. I disconnected both. I was going to fun troubleshoot it at some point as it was "fixed" when shining a light on the ambient light sensor. I have both touchbar components disconnected, as it was the only way to avoid the sudden crashes (even while plugged in). This sudden crashing was the reason it was no longer usable for my uncle, after complete reinstallations, a new battery.

I will have to measure the current when the touchbar is plugged back in and powered off. Do you think it's possible to connect one part without the other?

To me 30-40ma seems kind of high when the power adapter is plugged in and it's turned off...but this is my first macbook among many various laptops. Is that current normal when it's off? Thanks again for the info.

[gboone]

I rechecked R7063 and it's actually good. Today the usb meter is showing over 1A when battery is fully charged and the machine is powered off (It was around 500ma before). I can tell from the front of the board that U7000 is hot. I will post back with results.

[mon2]

Carefully measure the voltage to ground on F7000 (check both sides). You are checking the voltage of PPBUS_G3H. If the voltage is not in the expected range, remove all power. Flux and remove the fuse @ F7000 so you can isolate the PPBUS_G3H producer (ISL9240) & the consumer (downstream) side of this key power rail.

Then power up and check if the PPBUS_G3H voltage is of the proper voltage and if it is stable. Respectively, remove all power, meter in resistance mode, measure the resistance to ground of each leg of this removed fuse @ F7000. We are checking if there is a shorted part on either side of this isolated power rail.

Post each measurement. If U7000 is heating up, it is most likely under a heavy load. The worst case is when this high voltage rail leaks onto the CPU due to a high side mosfet leakage. Then the CPU is dead and this is a no-fix.