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CMOS Checksum Error

Posted on 1998-08-05
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Last Modified: 2010-04-26
My pentium 120 machine has started giving CMOS CHECKSUM ERROR every time it is powered up.  I can press F1 to proceed.   I have replaced the motherboard battery, which seemed to clear the error for a day or so but it has returned.   Any ideas ?
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Question by:communicado
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by:jom080298
ID: 1122337
may be cause of motherboard problem, contact your vendor ..
JOM.
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MATTCEI earned 50 total points
ID: 1122338
Since you have replaced the battery,i assume it's a button type - if not,let me know.Below applies to button type.

Get your hands on a volt-amp meter.Measure following with system power off:

Volts from case ground to battery positive clip (try not to push down on the clip - you don't want to accidently fix a poor connection).Volts should be around 3VDC.If lower,pull battery and measure it directly.If volts ok,one or both of connectors are dirty or loose (use rubbing alchohol to clean).If low,go to next step.

Measure amps through the 2 pins where the 'ERASE CMOS' jumper sits when it's NOT on 'ERASE CMOS'.Should be no more than ~50ua; but this depends on motherboard.I'd say ~300ua or more indicates a defective motherboard.If this is the case,let me know.It MAY be repairable.

By the way,if this jumper is already off,you've found your problem.

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Expert Comment

by:joe_massimino
ID: 1122339
After you have replced the battery have you entered CMOS and verified its settings, then save and exit?

If this does not fix your trouble, you may try moving the memory around to see if anything changes.  


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Author Comment

by:communicado
ID: 1122340
Thanks for the advise... Problem solved but in a roundabout way.  

Testing forced me to dig out the docs for the motherboard.  It turns out that the default state for the CMOS ERASE jumper is OFF.  I guess I had changed it in the early days of trying to figure this out and not replaced it back to the correct position.  I had checked the jumper when I replaced the battery but (wrongly) assumed that it should be ON.  

Just goes to show.....READ THE MANUAL !
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