your last lined is typed wrong, works, should be worked, (past tense) right?
I guess the screen is 100% dead and PC silent right? no text to the screen ever.
old laptops 15 long years old in fact (can be)
old pentium4 with a square 4:5 screen wow.
some fans are modulated, ever heard of PWM? (this one is)
so did you first remove relic old main battery first,
it will be shorted now, and when shorted it overoloads power buses.
then the coin cell is NEXT
, never seen one last 15 year, not me.
why wait get the HP RTC cmos coin cell. for 2 bucks and put it in.
dead PC 101, above done, fan dead.
1: power pack 19vdc, it must be at least 18.5vdc,
at the mobo not in hand by it self. the means under load testing.
normal load. we use a thing (20bucks) a voltmeter DMM to test all power packs. or replace it for $10 if you can even find one this old.
there is more lots more, if one component on the mobo shorts.
we can find that but , ill stop here, if you can get this far.
now the book on your PC, page 91 shows how to change the CMOS battery, here is the steps (compaqs are PITA)
this page. (Compaq then thought it lasted 20 years, hahahahaha)
Keyboard cover(page 2-13)
Speaker (page 2-15)
Keyboard (page 2-16)
Switchboard PCA(page 2-19)
CD/DVD (page 2-20
Display (page 2-23)
Top case (page 2-26)
Floppy (page 2-32)
Heat sink (page 2-40)
Motherboard (page 2-50) bingo the coin cell.
the fan is modulated. (it is controlled at all times for speed)
at power on most laps it run real fast first. then slows.
this is by DESIGN to keep noise lower.
id the CD does not eject try on damand there is no power.
if fan is dead, to, power is gone
one guy asked what power means. ok
it means all 3 4 or 5 power regulators on board work
1.8 and more, if any power reg shuts down the PC is DEAD.