One battery permanently at 0.0V

MNT Reform
1

Hi,

I had a serial console attached to my Reform and while doing so I apparently shorted something out or whatever… anyways I heard some zapping noise. I immediately turned off the device, removed the batteries, inspected the boards and everything looked OK.

Then went ahead and turned on without batteries. The device worked fine, so I went ahead and put in the batteries again. I noticed one battery shows 0V and was reported missing. I also have both LEDCHG1 and LEDCHG2 on. But no charge going to the batteries.

Inspected the board again and this time noticed R28 looks burned and indeed it measured 30 Ohms instead of the expected 4,7 Ohms. So I went ahead and replaced it.

Unfortunately, no avail, still the same.

I already tried:

  • switching around the batteries. It is always the same slot reporting as 0V, no matter which battery is in it.
  • checked connection from the battery holder to the mainboard, I have 100 Ohms to the respective LPC6803 input.
  • measured R12, R20, C11 (all in circuit) - all seem fine.
  • F2 seems fine.

Is there anything else I could check?

It seems most likely to me the LTC6803 has some kind of internal failure. Any idea how I could verify that before I try swapping it out?

Thanks and kind regards

1 Like
2

:partying_face:

What I like best about posting on a forum is it makes you think. Looked at the schematics again and finally found the trace for BAT5+ between J2 and J13 was burned. Fixed that and we’re back to working!

It is so awesome to have a laptop where I can just look at the schematics and actually repair things!

8 Likes
3

I had the exact same issue, shorted the battery terminal and saw the magic smoke appear. Checked the schematics and found your post, sure enough the BAT 5+ trace between J2 and J13 was blown.

Will definitely be removing batteries when opening the bottom in the future.

4

I also did this because I didn’t follow the advice to remove batteries before playing around inside…

I can also confirm for future magic smoke creators, that it is the two nearest pins that need to be connected. Rightmost of J2 to leftmost of J13. You can confirm with a multimeter that J2 pin 5 goes to ground, and J13 pin 1 goes to the nearby fuse F2.

I’m very unskilled in soldering so I couldn’t bridge the pins, so I snipped the battery cables and did the join there. I apologize for my inelegant solution. :smiling_face_with_tear: