X31 Charging circuit problem

[lantian]

Hi guys, I have some troubles with my X31 (2673-RG6). After the battery gets fully charged, the power circuit should switch to ac power only, but it doesn't. It starts randomly switching between battery and ac mode and a high pitch noise appears (like from LCD inverter, with faulty coil, but mine inverter is ok). When I try removing battery and get the laptop running on ac only, lcd starts to dim randomly as the acpi starts switching power saving modes. I looks like the laptop switches to performance mode only if CPU usage is above 10%. I tried disabling Intel SpeedStep and all power saving features. I also upgraded BIOS and Embedded controller software to latest version possible.

I assume it is not a software related problem, cause i tried several systems with latest possible drivers (inc. Linux, FreeBSD, Windows 7 and XP) and after the acpi driver gets loaded the problem with power circuit appears once again. Maybye the coils in power circuit are bad (like these in T23 series). I've recently bought and installed a new miniPCI wifi card (MikroTik R52) instead of that old Cisco Aironet, it is a standard (no high power) card and the problem with battery and acpi shows either with or without miniPCI card installed.

So, if there is some thinkpad hw guru, i would really appreciate any advice on this topic...

[jronald]

I have one just like it. After stripping everything out it still does it. [censored] annoying!

Ron

[lantian]

Well thanks for answer. I found similar problems on asus eee forums and it was the coils as i stated above..

Also I noticed, that the problem is maybye temperature related, so it could be the coils. Will try to strip entire laptop to bits and mess around with that coils. Hope it will be only cold wire or something..

[lantian]

Bump. Still desperate.. It looks like I should get a new motherboard for my X31..

[jronald]

Hey, throw it in the freezer and see if it charges.

Ron

[lantian]

Tried throwing it into fridge, it worked for couple minutes, but after that, same problem.

Anyway, I've done some research and it look like one of main MOSFETs have bigger leakage on DS diode than others (according to datasheets).

Similar problem has been solved here: http://thinkpads.com/forum/viewtopic.ph ... 6&p=586873

Is there some good source of spare SMD MOSFETs (for Europe ??

[ilesoft]

Hi,

Did you get your motherboard fixed?

I have quite similar problem, but it has something to do with either heat or low current.

On idle use my X31 won't charge the battery at all. If I put some stress on the laptop, for example start a program or drive HDD defragmenter, the laptop starts making sounds like the AC adapter is connected and then disconnected. If I put a lot of stress on the laptop, for example a program that uses all the CPU capacity, all works ok. The battery charges, no AC plugging / unplugging sounds appear and the screen stays at its full brightness. Also the high pitch noise coming from the coils around the DC jack disappears. When I stop stressing the CPU, the problems reappear immediately. So from my point of view it's not a heat issue. I have also tried pressing down on the coils and motherboard from different points, but flexing the mobo doesn't seem to have any effect.

The battery and AC adapter are both ok. tested with another X31.

Does anyone know what component could be the faulty one? I have one other X31 with a dead GPU, from whose motherboard I could borrow spare parts.

[lantian]

Well, unfortunately no. I have been playing around with MOSFETs around the power cord and replaced a few but with no luck. Finally I have ordered replacement MB from ebay..

I can send you complete circuit diagrams of X31 boards if you want.