On 11/16/2012 3:59 PM, Michael A. Terrell wrote:

Karl Townsend wrote:

On Fri, 16 Nov 2012 17:53:26 -0500, "Michael A. Terrell"
wrote:


Karl Townsend wrote:

i had a CMOS checksum error on my CNC mill. So, I installed a new
motherboard battery. Now the CPU fan just comes on and it makes no
attempt to boot. Is the computer DOA? I checked connections and
wiggled stuff.


Remove the new battery& short out the socket for a few seconds, then
reinstall the battery. You may have some corrupt data in the CMOS
scratchpad RAM.

tryed that, No Joy


Try another power supply, if you have one. You may have a dying or
dead motherboard. Unplug all the drives, and cards except the video
card, if it isn't part of the motherboard. If you can't get the bios
screen to flash, look at the electrolytics on the motherboard, and the
ones near the processor in particular.

If they are bulging, they need replaced, or replace the motherboard.
They are a special low ESR 105° C type capacitor, and not always easy to
replace, because they are soldered to internal layers. If you can find
the exact same type motherboard, and move the processor to the
replacement board you shouldn't have to reinstall any software.

How did you determine that the unspecified cnc mill with the unspecified
controller running an unspecified OS with an unspecified user interface
made no *attempt* to boot?

If it's an IBM-PC compatible controller with a keyboard and display
and you don't get any beeps and you see nothing on the display and
entering the BIOS setup pre-boot keystrokes at the proper time don't do
anything, yep, you've probably borked it.

If it's the typical coin-cell non-rechargeable CMOS battery, there's
a diode in series and shorting the socket does nothing. You have to
WAIT, I'd give it an hour before you give up and replace the motherboard.
There may be a jumper to reset the cmos, but it may only open the circuit
and also require you to wait. Shouldn't take an hour, but what do you
have to lose by waiting longer.

Also, did you unplug the computer while you waited?
Many computers have a 5V supply that's hot when the power is off
and may prevent the CMOS from resetting. It's also possible that
there's enough power coming back thru an I/O port to keep the CMOS
alive.

I had a situation where there was enough juice coming back through
a GPIB port to keep the GPIB fully functional with the power
to the microcontroller removed. I unplugged it and it just kept
on running. Thought I'd been possessed...