TM290 - Can empty CMOS batteries cause trouble?

Hallo,
i have an Acer Travelmate 290 that barely starts these days. Fan is starting properly but screen remains black. Sometimes the bootscreen appears and then the screen goes white after some seconds. I can go into BIOS or run Memtest+ for some seconds but it always gets white some time later. I removed all modular parts and exchanged RAMs already. It got worse lately. Whereas the device starts maybe one of 10 attempts and remains stable for seconds it was working for minutes weeks ago. I detached/disassembled the notebook completely already several times. I don't have any Pentium-M replacement so this is the only part i couldn't swap yet.

I measured the cmos coin cell. It holds 2.539V of 3.0V. Looks empty but CMOS values are still ok i think (date is correct if i enter BIOS). Is it possible that the CMOS cell is responsible for those false starts?

My CMOS cell replacement thread:
forum.notebookreview.com/showthread.php?t=322144

 

If you don't lose the time, the CMOS battery is fine.
Even if it was dead, it could not cause problems like this, unless you were losing some setting like a higher, non stock memory voltage (which is not the case here, so I should just say it definitively, that is not your problem).

Sounds more to me like a video issue.
How is the system when hooked to an external monitor? If it works, it's either the LCD, inverter, or connection cables. If it doesn't, it's probably the GPU, which is likely part of your motherboard.

Personally I think it's the inverter or the GPU.

 

Yeah we had a thread here not long ago with similar issues and as it turned out - it was the LCD's fault. So maybe @Hep! is right..

 

I will solder the old battery back in and try the laptop on an external display.

If its the GPU or inverter there's nothing i can do but changing the PCB, right?
Btw, where is the GPU? The green chip near the CPU socket (picture attached)?

img3.imagebanana.com/img/ues545z1/AcerPCBUp.jpg
Sorry for the hassle, i'm not allowed to post direct links yet.

 

If the laptop works fine with external display that would mean your GPU is fine and the problem is your LCD...

 

You shouldn't need to put in the CMOS battery at all to get the laptop booting. If it's the power inverter, that's an easy replacement, which is only about $40 - $60 USD usually. If it's the GPU, you may be able to find a replacement board for 100-500 USD, depending on where you get it and availability/demand. If the price is too high, I would just get a new laptop (especially since it's an Acer >_>) That green chip is your northbridge which in this case, is also your graphics accelerator.

I did a quick ebay search and found this board if it comes down to that: http://cgi.ebay.com/Acer-Travelmate...mQQptZAU_Laptop_Parts?_trksid=p3286.m20.l1116
Worth fixing if this turns out to be the problem, IMO.

 

Good hint. I've seen ppl on eBay with white screen problem as well. They pretend to stick something under the display to fix this temporarily. But the white screen is not my primary problem at the moment. The laptop doesn't start anymore. Currently there is only a fan start and black screen. CRT is black as well. I hope it comes up again soon. I'll charge the battery in the meantime. Maybe it runs better in this mode.. don't know.

I would spend up to 100Eur to fix the laptop i think.

 

Hmm.. are you sure it should run without cmos battery? Any chance that it does not? I can't get it on anymore. TFT remains completely dark, DVD tray doesn't open and its led (dvd) on system led bar is permanently on. Pressing (FN) Key lids up another led temporarily.

Seems it gets worse over time like if cmos battery goes down slowly. Now that its removed completely nothing works anymore.

But yes, it did that before already...

Tomorrow i'll solder some cables to the cmos battery pins leading out of the case for power measurement and easy access. Its unreachable from outside and i always have to disassemble the whole device to reach it.

 

Yes, CMOS battery is not an integral part of a POST....
Dead motherboard.

 

i know this is going to sound a bit stupid but here goes.
remove power cable
remove battery
reset laptop(hold down power for 30 seconds)
now replace power not the battery
then restart laptop without the battery.

let us know if you have any joy.

Phil