onboard VGA port disabled

NewToFPGA wrote:
>> Two things:
>>
>> 1) Did you follow my suggestion, and unplug the computer before following
>> the procedure in the manual ? Removing all the cables inside the computer
>> is not essential, but making sure there is no +5VSB is a good safety
>> precaution. And for that, I tell people to unplug, so there is no
>> ambiguity in the instructions.
>
> The computer was unplugged for a week or so before I changed the
> jumper settings. I moved the jumpers to pins1-2 while there is no
> power supply. Then I connected the power supply. There was no
> activity. After that I tried to put back to the pins 2-3 while the
> power supply was unplugged. Then put the supply back on. Still
> nothing...
>
>
>
>> 2) Did you put the CMOS jumper back onto pins 2-3. That is the "normal"
>> position for the jumper. On some boards, the jumper is needed so the
>> CMOS well can get power, so it has to go back in the "normal" position.
>>
>
> I had the jumpers on pins1-2 when I plugged in the supply.
>
>> If the jumper was placed on pins 1-2, while power was applied, on some
>> boards that burns a small dual diode.
>
> I dont see K45 or BAS40W-05 dual diode in the manual. I will see if I
> could locate it.
>
>> I hope your problem is you just left that jumper off entirely.
>
> I have the jumpers back on pins 2-3. What do u mean by "jumper off
> entirely".
>
> what is my next option? any idea?
>

There are three options for the header:

1) Jumper on 1-2 (only with computer unplugged - potential for damage otherwise)
2) Jumper on 2-3 (safe whether powered or not - the normal jumper position)
3) Jumper removed entirely - would cause CMOS well to get no power.
AFAIK, this is safe in terms of damaging a K45. Not sure about
other side effects.

My guess is, you may have damaged the dual diode, by powering the system
while the jumper was in position 1-2. I have no way to back up this
claim, as the motherboard designers have options as to how they
design this circuit. So a motherboard may have this exposure or it
may not.

In terms of its location, examine the following area. There is the CMOS battery
on the right of the area. The JP2 jumper bounds the bottom of the area.
The Southbridge chip bounds the left side of the area. In that roughly
one square inch of area, look for a black device, as tiny as the jumper
plug, with three legs. That could be the K45 device. Outer dimensions,
contacts included, would be 2mm x 2mm. (I cannot find a picture of the
motherboard, with sufficiently high resolution, so you'll have to look
for it.)

To repair it, you need to know something about electronics, and need to
know how to solder.

Mouser.com has a reasonable likeness to the part. Mouser part number 621-BAS40W-05-F

http://www.mouser.com/Search/ProductDetail.aspx?qs=oQbAKJL2WnGYQHmpyFm5iA%3d%3d

The datasheet for that diode is here. My copy of Acrobat complained a bit
trying to read this, but it is readable. When replacing it, note the orientation
of the device. Make sure the "K45" logo is facing upwards. Two numbers in
slightly smaller font (if that is possible), indicate the month and year of
manufacture.

http://www.diodes.com/datasheets/ds30114.pdf

First you have to locate the part (and not mistake it for one of the many
other potential transistor devices that might also be on the board). As
I mentioned before, I have three boards were I verified the marking was
K45 on each one, so the BAS40-05 is a popular solution for the power
ORing diode. What the dual diode selects between, is 3V from the CMOS
battery (through a 1K ohm limiting resistor) or a 3V source derived
from +5VSB (with no limiting resistor in the path). The fact there is
no limiting resistor, is how the damage happens. (Assuming the motherboard
is designed the "dangerous" way.)

It is also possible a coincidence happened, like the power switch cable
fell off, you forgot to plug something in, etc. So my analysis is not
guaranteed to be the only failure mechanism.

Paul

NewToFPGA wrote:
> I dont find the K45 anywhere near the CMOS battery. I all see are
> starting with R, C, ST, ....
>
> I had to change the power supply before a week ago. Do you think it
> has happened again?

Well, there is a trick you can use, to make a power supply run.
Connect PS_ON# to COM. Wiring diagrams and colors are documented here.

24 pin
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

20 pin
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf

The PS_ON# signal is open collector. Or is supposed to be. The power
supply input signal, should have a pullup on it. The motherboard pulls
that signal to ground, to make the PSU fan spin, and cause all main outputs
to appear. You can connect PS_ON# to COM, and make the PSU run.

The dangers with such a technique.

1) The PSU only runs, as long as there is a wire from PS_ON# to COM.
So if there isn't a good connection, the computer could stop or reset.

2) Computers have overheat protection. If the computer overheats, it has
the ability to turn off the computer. But if you use a jumper to keep
PS_ON# going, then the computer has "lost control". It is no longer
in charge of "switch on" and "turn off". So you lose a protection feature.
If the CPU overheats, while you have left the room, then the CPU could fry.

So the technique will work, but is not the safest thing to do. By defeating
safety features, you increase the odds of something bad happening. But you
can certainly try this for a temporary test. (Connect PS_ON# to COM,
see the BIOS screen appear, then switch off again by removing the shunt.)

If this was my computer, and it wouldn't go, this is the test case I would try.

1) Remove motherboard from computer case. That avoids accidental shorts to the
bottom of the motherboard, as a cause of the failure.

2) Remove processor and RAM from the motherboard. Pull add-in cards.
You want the motherboard, power supply, power switch to PANEL header.

3) If the motherboard has a green LED to monitor +5VSB, verify the LED lights
up when the power supply is switched on at the back. If there is no LED
(a cheap motherboard), then use a multimeter to verify +5VSB is present.
If not, find out why.

4) Press the front power button. The motherboard logic circuit, powered by +5VSB,
should be asserting (grounding) PS_ON#. The power supply should start, and
the fan should spin. Since both processor and RAM are missing, it cannot
boot. There is no video card or other cards present either. So there is
nothing to see. The whole purpose of this test, is to verify that the
motherboard could turn on the power supply. If the test passes, add
components one at a time, and carry out additional test cases, until a
failure is again observed.

I've built up my last two computer systems completely on a table, without
mounting them in a computer case. That allowed me to add a component at a
time, and verify it worked. I even installed the OS and got the Windows
desktop, while all the stuff was sitting on the table. It is a lot easier
to see what you're doing, with the motherboard out in the open. The only
danger, is there is no way to keep the video card secured in its slot, so
you have to be extra careful to not tug on the cable. If you have small
children in the area, this is not a good test to do.

HTH,
Paul