cmos checksum error

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Em1 · #1 Post by **Em1** » Tue Mar 04, 2008 1:40 am

I am getting a cmos checksum error at startup. So I changed the cmos battery but still get the same error.

The main problem is that a/c power is not recognized so the laptop is running exclusively from the battery. Any suggestions on what it could be?

#2 Post by **rkawakami** » Tue Mar 04, 2008 2:08 am

Can't say that one thing is affecting the other. However, if there's a major power problem with the motherboard I suppose it could result in a BIOS error. If you can access the BIOS setup page, I'd try loading the default settings and see if that helps. Was there anything done to the system recently which might have caused this problem (i.e., BIOS or Embedded Controller update, installation of new hardware, general fooling around with the motherboard, etc.)?

Em1 · #3 Post by **Em1** » Tue Mar 04, 2008 10:22 pm

Nothing was done to the system. This just happened a couple days ago out of the blue.

I loaded the defaults but the a/c power isn't recognized and now it just sits at a blank screen and doesn't load up fully [like it was doing before].

#4 Post by **rkawakami** » Tue Mar 04, 2008 10:41 pm

The BIOS can be re-loading with default settings by doing the following:

- power up the system, holding the F1 key to access the BIOS
- from the main menu, using the arrow keys, select the "Restart" option
- again, with the arrow keys, select the "Load Setup Defaults" line
- press the Enter key
- confirm the change

That will load default settings, which may not be what you like to run for your system (e.g., the serial port will be disabled preventing use if you ever boot a DOS program on a floppy). Go through the other menus and verify everything is the way you want it. Restart, saving the changes. That should fix whatever problem you had with the bad CMOS battery.

The problem with your system not working off of the AC adapter could have a couple of sources:

- bad AC adapter; use another known working IBM 16V 4.5A adapter or measure the voltage at the DC plug
- blown fuse on the motherboard; much harder to fix but it can be done with the right tools (25W soldering iron, tweezers, good eyes)
- other power system components on the motherboard; extremely hard to determine which part(s) are bad since circuit schematics are not available

Most likely, the best course to "fix" the problem if it's one of the last two, is to replace the motherboard.

Em1 · #5 Post by **Em1** » Tue Mar 04, 2008 11:58 pm

I loaded the defaults and saved and exit but it doesn't restart. It just sits on a black screen with the battery light blinking.

#6 Post by **rkawakami** » Wed Mar 05, 2008 12:44 am

Hmm... sounds like a major bug with the motherboard. Can you power off and re-boot?

Em1 · #7 Post by **Em1** » Wed Mar 05, 2008 1:13 am

I cannot. I have to pull the battery. This is something I've done recently, it just started during this process.

#8 Post by **rkawakami** » Wed Mar 05, 2008 2:45 am

Holding the power button down for at least 10 seconds does not make the system go off?

Is this a T2x or T30 system? Actually, maybe it doesn't really matter. How about this: remove all of the excess hardware from the system and then try turning the laptop on. By that I mean the memory, the hard drive, any MiniPCI card (modem, wireless or combo), ethernet and Ultrabay device. Does it generate a 1-3-3-1 beep sequence? If you don't get that beep sequence, then there's a problem on the motherboard which may not be easily resolved. If you do get that beep code, can you then turn the system off with the power button (and not by removing the battery)? If yes to that, then install ONE memory stick and boot the system again. See if you can access BIOS normally. If you still get a 1-3-3-1 beep code, try another memory module or move the first module into the other slot. What I'm basically trying to do is to see if you have a problem with any particular piece of hardware which may be giving you "power" problems. A small likelihood but one that I think needs to be eliminated.

You should also attempt to verify that your AC adapter is functional. Either measure the output voltage of your existing adapter with a voltmeter or try another one which you have a high degree of certainty that works. I hesitate to recommend that you plug your adapter into another Thinkpad on the small chance that it's providing more that the normal 16 volts and does something to that system.

Em1 · #9 Post by **Em1** » Thu Mar 06, 2008 10:25 pm

I can't really run anything because my battery is dead so it starts up and immediately gives me a critical battery error and shuts down.

Is there a way to test the a/c adapter?

#10 Post by **rkawakami** » Thu Mar 06, 2008 10:44 pm

The only way I know of verifying that the AC adapter is delivering the proper voltage is to measure the output with a voltmeter (aka, multimeter). It's much harder to determine if it will supply the rated current, but there's a good chance that if it reads 16VDC, then the adapter is working properly. You can get a cheap multimeter at Radio Shack, Frys or most hardware stores.

By the way, please update your profile with your location (city/state). It can help in cases like this where we can point you to some local resources.

Em1 · #11 Post by **Em1** » Thu Mar 13, 2008 8:25 pm

I ordered a new a/c adapter (hoping it would solve my problems)...and it did. Thank god. I'm up and running now. Thanks for all your help.

cmos checksum error

cmos checksum error

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