How can i reset CMOS ???

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View

First of all, sorry for my english !!!

The pc can't start. Led are ON, but the pc doesn't start. The monitor
is off, no signal.

THe pc doesn't make any beep.

I think there is a mb problem and i want to reset the CMOS setting.

I try to remove the battery fro one day, but these action have no

I try to change the position of the jumper near the battery (with pc
off) but nothing change.

There is anyone that has had the same problem and he has resolved it.

The pc is an ACer Aspire m3640, the motherboard i think is a Foxconn
(but i'm not sure)

Thanks !!!!!

Re: How can i reset CMOS ???

Francesco wrote:
Quoted text here. Click to load it

Did you check the battery voltage ? Either replace the battery, or
check the battery with a multimeter. A CR2032 should read at least
3.0V when it is new, and if the voltage drops below 2.4V it should be

Also, verify that you haven't pulled loose the power switch cable
leading from the front panel of the computer, to the motherboard.
There are a number of cables, that plug into the PANEL header,
and one pair of wires goes off to the power switch.

Since you've removed the CMOS battery, with the power cord of the
computer unplugged, you've already cleared the CMOS. If the
computer has all power removed, and the CR2032 battery is removed
as well, the CMOS settings would be lost. And that is what
resetting the CMOS does as well. So you've already done it.

And that is why I suggest checking the CR2032 battery voltage
next, in case that battery is flat (zero volts). Some computers
(but not all) will not start if the battery is dead.


Re: How can i reset CMOS ???

Quoted text here. Click to load it

Consider that there is a problem with the power supply. PS's quite often can
fail partially so that you can still have LEDs lit or a cpu fan running, but
have other sections of the PS fail to not give enough voltage to allow the
cpu, graphics, hdd, etc to function.
Jan Alter

Re: How can i reset CMOS ???

Thank you for replying !!!!

Quoted text here. Click to load it

Battery checked. 3V

Quoted text here. Click to load it

I dont' understand, probably for my bad english.

There is many wires from the front panel and they are all 'linked' to
the mb

Quoted text here. Click to load it

To verify that what can i do ?

Using multimeter whith the 24 pin coonection ?

Thank you to all !!!!

Re: How can i reset CMOS ???

I have tested the voltage.

The only anomaly is the voltage o f the blue cable that is -11 instead
of -12V.

The other voltages are major than expexted.

For example 3,37 ; 5,04 ; 12,01

I try to start the pc without any video card and after removed all
memory banks, but again the fan start but no beep

Mother Board ?
Processor ?
Power supply ? i think no after last test

Re: How can i reset CMOS ???

Francesco wrote:
Quoted text here. Click to load it

These are the various versions of the ATX power supply spec. The last
one is for 24 pin power supplies. The first two are for 20 pin supplies.
The first specification, is from the days when -5V was still included
on power supplies.
(page 27) (page 30) (page

Did you check the PWR_OK signal ? It should be logic one (2V to 5V) when
the power supply is running. If the signal is logic zero (0.8V or less),
then the power supply is saying it isn't ready. The power supply may
give the voltages, but not give PWR_OK. And that may prevent the
motherboard from coming out of RESET state.

So unlike your previous post, now you're saying the power supply is
running. Or, did you start the power supply on your test bench,
by shorting PS_ON# to COM ? If the power supply is now running, and
the system won't start, that could be a stick of bad RAM. If there
is bad RAM below 640K, it may affect the ability of the BIOS to do
things. I had a problem here, were there were no beeps, and it was
a stick of bad RAM. In theory, the BIOS should be able to start, without
functional RAM, but that doesn't appear to be the case in practice.


Re: How can i reset CMOS ???

Quoted text here. Click to load it

I cheched the PWR_OK signal. The grey cable. ANd the voltage is little
over 5V, 5.10 about.

Quoted text here. Click to load it

The power supply is running. I started shorting PS ON to COM only for
testing power supply.

The power supply is atrting even with the switch on the front panel.
When I press the switch, the led on the front is lighting, the fan (all
the fans, cpu fan, video card fan, pc fan) start, but the monitor say
'no signal' and the mb doesn't beep. I try removing vga card and using
integarted vga but nothing.

Quoted text here. Click to load it

Few weeks ago i changed one bank of RAM cause many blue screen under
windows with one new bank of 2 GB memory that i think works well, until

I try changing bank but the pc doesnt' work again

Maybe motherboard crash, or processor crash. I hope no!!!

If you have any new idea please send to bewsgroup!!!!

Thnks a lot for your help!!!!!!!!

Re: How can i reset CMOS ???

Francesco wrote:
Quoted text here. Click to load it

Try removing all the RAM (while the power is turned off on the back of
the computer). Then, turn on the computer and listen for "beep" codes
from the computer case internal speaker. If you hear "beeps", it means
the CPU was able to read some BIOS code. If the computer is silent,
with no beep codes, then the CPU cannot read the BIOS. Either the CPU
is dead, or the BIOS is corrupted, or there is some other onboard
regulated voltage which is not working properly. It could be a
motherboard problem for example. CPU chips hardly ever fail and
are very reliable.

A good technique for troubleshooting, is to gradually disconnect
unnecessary hardware, and watch for a change in the symptoms. For
example, you can unplug the disk cables, in an attempt to get the
BIOS working.

The minimum configuration I'd use, would be

    motherboard, CPU, front_power_switch, computer_case_speaker, power supply

That should be enough to test for "beeping" of the computer speaker, because
of missing RAM sticks. If a motherboard and CPU won't work, then try
another motherboard. You've already tested the power supply, so that might
not be the problem. The motherboard could have a problem. But
simplify the hardware setup, before taking the system all apart.


Re: How can i reset CMOS ???

On 1/15/2010 9:37 AM, Francesco wrote:
Quoted text here. Click to load it

Maybe you DID reset the CMOS but, because the computer does not POST, you
cannot tell. As someone else wrote, your problem could be the power supply.
If you have not changed anything else in the computer recently then the PS
would be the first thing I'd try.

Site Timeline