No video output after reset the computer motherboard

[wo918]

Hi all,

I suspect that something was wrong with my motherboard, so I reset my
motherboard to clear the CMOS by shorting two special pins according
to the instruction of my motherboard. But after this, my computer
can't output video signal any more. My computer can power up, with no
beep. Any ideas on what's wrong? and how to solve it?

 

[Thomas Wendell]

Hi all,

I suspect that something was wrong with my motherboard, so I reset my
motherboard to clear the CMOS by shorting two special pins according
to the instruction of my motherboard. But after this, my computer
can't output video signal any more. My computer can power up, with no
beep. Any ideas on what's wrong? and how to solve it?

Please tell us what motherboard, gfx card?
(If mb has onboard video, and you've installed a video card, the signal
migth come out the wrong connector, depending on card type (PCI/AGP/PCI-E))



--
Tumppi
=================================
A lot learned from these newsgroups
Helsinki, FINLAND
(translations from/to FI not always accurate
=================================

 

[wo918]

Please tell us what motherboard, gfx card?
(If mb has onboard video, and you've installed a video card, the signal
migth come out the wrong connector, depending on card type (PCI/AGP/PCI-E))

--
Tumppi
=================================
A lot learned from these newsgroups
Helsinki, FINLAND
(translations from/to FI not always accurate
=================================

Hi,

Thanks for the reply. The motherboad is Asrock M863G, with on-board
video (SIS741) and audio chips), no standalone video and audio cards.

 

[Mike T.]

Hi,

Thanks for the reply. The motherboad is Asrock M863G, with on-board
video (SIS741) and audio chips), no standalone video and audio cards.

Stupid question. After you shorted the two pins to clear the cmos, using
the little jumper, did you put the little jumper back in the normal/run
position? Typically, this jumper will use three pins. For example, short
pins 1-2 with jumper, this is the normal/run position (just an example, pins
might be different on your board). Short pins 2-3 with the jumper and this
is the CLEAR CMOS position. (just an example, pins might be different on
your board)

If the jumper is still in the clear position, system will not POST, and you
will get no video. -Dave

 

[wo918]

Stupid question. After you shorted the two pins to clear the cmos, using
the little jumper, did you put the little jumper back in the normal/run
position? Typically, this jumper will use three pins. For example, short
pins 1-2 with jumper, this is the normal/run position (just an example, pins
might be different on your board). Short pins 2-3 with the jumper and this
is the CLEAR CMOS position. (just an example, pins might be different on
your board)

If the jumper is still in the clear position, system will not POST, and you
will getnovideo. -Dave- Hide quoted text -

- Show quoted text -

don't think the people who asked a question here are all stupid! Of
course I've set the jumper back to the NORMAL position, but there is
no video output signal. You are not as clever as you thought,
unfortunatelly.

 

[JAD]

Integrated graphic disabled in bios now?

don't think the people who asked a question here are all stupid! Of
course I've set the jumper back to the NORMAL position, but there is
no video output signal. You are not as clever as you thought,
unfortunatelly.

 

[Paul]

don't think the people who asked a question here are all stupid! Of
course I've set the jumper back to the NORMAL position, but there is
no video output signal. You are not as clever as you thought,
unfortunatelly.

When I search on that motherboard number, for some reason I end up at PCChips.
Anyway, I downloaded this manual.

http://64.124.27.138/pcchips/manual/863AG_G_v51B.pdf

When you did the "clear CMOS" procedure, was it with the +5VSB removed from
the system ? What I recommend to people, is to unplug the computer, before
using the jumper. There are a fair number of badly designed motherboards,
where using the jumper, while +5VSB is still active, results in an "ORing
diode" getting burned. The diode is a dual diode, looks like a small three
lead transistor, and selects current from the CMOS coin cell, or selects
current regulated down from +5VSB. What seems to happen, is the jumper shorts
the line to ground, and if +5VSB is still running, the jumper actually shorts
that rail to ground, through the dual diode. Most manuals will tell you to
unplug, as the first step in "clear CMOS". And because there is no way to
predict how bad the designs are, it is a good practice for any motherboard.

http://www.diodes.com/datasheets/ds30114.pdf (example diode BAS40W-05)

If you aren't getting any beep codes on the speaker, then chances are the
processor isn't able to read instructions out of the BIOS EEPROM.

You could try clearing the CMOS again, but this time, unplug the computer,
pull the CMOS coin cell battery. Then move the jumper to the "clear" position
for a minute, then move it back. Reinstall CMOS battery, plug in and try it
again.

It is possible, if the ORing diode was completely burned, that the CMOS well
on the Southbridge might be completely unpowered now. But then you might get
weird symptoms, like the computer starting, as soon as the power is
switched on, on the back of the computer. The diode in question is so small,
I have to use a tiny magnifying glass to read the "K45" printed on the top
of it. When the diode burns, the legend on top is usually unreadable.

Paul