"Brad" wrote in message
...
Hi,

I have a Compaq Presario 1200XL110 laptop (bought 2nd hand) with
bad display (display "wires" disconnected). I used an external Monitor.
I
kept the laptop plugged into AC all the time and the battery installed.
I
had no problems the first few days. Note: the laptop was on from 7:30AM
until around 5PM every day. Then one morning, I tried to turn it on, but
absolutely nothing happened. The only indicator that was lit, which
is always lit, is the plugged into AC indicator. Note: I am a TV, etc.
(not
computer) serviceman. I won't go into details of the tests I performed,
which
included testing the power switch.
.
I removed a dead (!!) RTC/CMOS battery. Note: When the laptop
"worked",
there was no sign (loss of time/date) that the RTC/CMOS battery was going
bad.

I put this laptop in a box (main battery removed). About 5 days
later, I
hooked it up to AC, but left the main battery out (RTC/CMOS battery
removed).
When I tried to turn it on, absolutely nothing happened so I put it back
in
the box (main battery removed).

Over a month later, I hooked up the laptop (main battery removed & no
RTC
battery). When I pressed the power button, it booted up!!!!!!! I
repeated
shut down and power up. It boots up every time, although I see a warning
message caused by no RTC/CMOS battery. I installed a new RTC/CMOS
battery. I now use it on AC without the main battery installed. When I
shut
it down for the day, I remove AC power via the switch on the power strip.

Can someone explain this MYSTERY???


rare
I have seen a few machines act erratically with a cmos voltage around 2.3
volts or so.
A low but not completely discharged cmos battery could conceivably hold the
bios in an illogical state.

If you still have the old battery...
measure the voltage