Pc starts and runs but wont boot up monitor shows no signal
1) When you turn on the computer, watch and listen for:
a) power supply fan, (power is on)
b) chassis lights (power is on)
c) ticking sound during memory test
(the BIOS POST is running)
d) beeps or rhythmical error codes
(POST failed, bad CPU, CHIP set, memory or video)
e) Monitor either comes on, displays garbled video,
displays a No Sync or No Signal message...
No depending on how far it gets:
Check power supply, cables etc.
Check video cable.
Check monitor with a different PC
Now unplug the power cord, with the computer still
on, this will help drain any internal capacitors.
Wait 5 minutes, then shut off the switches,
and open up the box. try the following,
one at a time:
2) Remove all I/O cards except the video card,
and don't plug them back in until the problem
is fixed. Unplug all the ribbon cables from
the mother board as well:
Hard drives, CD drive, floppies etc.
Make sure you make notes about how to plug it
back in, and cable orientation !!!
0) Re-seat all power cables: Red, Black Yellow harnesses.
1) Unplug and re-seat the video card
2) Similarly, re-seat all memory SIM/DIM modules,
3) Re-seat the CPU
4) Replace the video card
5) Replace memory, CPU or whole mother board,
Plug the good parts back in one at a time,
and test the machine.
Save for the power supply, there really is NO way to test
and isolate a bad module except by swapping/ trial and error
because of inter-dependencies.
For example a bad I/O card, any I/O card, can short circuit
the I/O bus, causing all other plug-in cards to stop working,
or even the main mother-board to freeze during the POST.
A bad power supply ditto.
A bad memory chip ... ditto.
The type of electronic instruments required to actually
test modern computers running at Gigahertz speed cost
hundreds of thousands of dollars, some cost millions, and
are only available to hi end manufacturers
Even the power supply will not power up for a voltage check
if the mother board is bad, although you can use a jumper
on the green wire to ground to force it on, when you unplug
the power connector from the mother-board, if you are brave.
Computer shops carry a lot of spare parts, and their service
department has gutted computers rigged up as test jigs.
They trouble shoot your system by either plugging your
stuff into their jigs, one at a time, or by plugging known
good components into your computer until the problem
This if of course possibly dangerous, since one bad part
can also fry other good parts that plug into it, or that it
plugs into. The compute shops, of course charge you
enough to make up for this.
If a computer is partially operable, it is also possible to
run software diagnostics.
If not, swap and pray is the only way.
Hope this helps
Please rate my answers, martin.
Jun 25, 2008 |
HP PC Desktops