MB problem

[lewmur]

I don't think there is anyway around this but I thought I'd ask anyway. I have client with a MB with a bad keyboard socket. The board worked with a USB keyboard until the client reset the CMOS. Now it stops saying invalid CMOS, hit F1 to continue or F2 to load defaults. But the USB keyboard isn't active at this point on this MB.

[zlim]

The board worked with a USB keyboard until the client reset the CMOS.

Reset to default? If not, is is possibly to reset to default by shorting or removing the battery? This might set it back to use the bad PS/2 port but since it isn't working at present, I don't think you have much to lose.You can't do anything from what I've seen on a computer that doesn't recognize a keyboard. I'll keep looking to see if someone discovered something that worked.

[lewmur]

Reset to default? If not, is is possibly to reset to default by shorting or removing the battery? This might set it back to use the bad PS/2 port but since it isn't working at present, I don't think you have much to lose.You can't do anything from what I've seen on a computer that doesn't recognize a keyboard. I'll keep looking to see if someone discovered something that worked.

Thanks, but reseting to default is what caused the impass. So long as the computer was booting, the USB keyboard worked. But reseting the CMOS caused the F1 or F2 screen. The only way, that I know of, to get pass the F1 or F2 option is to use the PS2 keyboard and that's broke.

[V.T. Eric Layton]

Rather than lose an entire motherboard, why don't you de-solder a keyboard socket from a junker mobo and re-solder it onto this mobo? It's not difficult at all as long as you have moderate soldering skills.

[lewmur]

Rather than lose an entire motherboard, why don't you de-solder a keyboard socket from a junker mobo and re-solder it onto this mobo? It's not difficult at all as long as you have moderate soldering skills.

I once had very good soldering skills. But at 70, both the eyesight and shaky hands have taken their toll. :"> I'm afraid the board would wind up a charred mess! And I don't even own a soldering iron anymore that would be capable of the job. All of which gives me the excuse not to be bothered with something I no longer have the patience for anyway.

[zlim]

Lesson learned: if the keyboard PS/2 port breaks DO NOT reset the CMOS.Now all I have to do is remember that bit of advice!

[V.T. Eric Layton]

I wish you were in the neighborhood, Lew. I'd be happy to take care of it for you.

[b2cm]

You can try fixing the Ps/2 port (blown fuse that should be replaced). Or you can have a custom bios made that enables by default legacy support for USB keyboard.Liz,Add this to your tips: Do not plug or unplugged a PS/2 keyboard or mouse when the computer is on.

[lewmur]

You can try fixing the Ps/2 port (blown fuse that should be replaced). Or you can have a custom bios made that enables by default legacy support for USB keyboard.Liz,Add this to your tips: Do not plug or unplugged a PS/2 keyboard or mouse when the computer is on.

Thanks. I may no longer be capable of soldering the whole socket assembly, but I should be able to replace a fuse. Assuming I can find it.

[zlim]

b2cm, that fact is engraved in my memory (along with don't format C or run rm -rf). There are a few things I still know enough NEVER to do. Thanks for mentioning it.

[lewmur]

You can try fixing the Ps/2 port (blown fuse that should be replaced). Or you can have a custom bios made that enables by default legacy support for USB keyboard.Liz,Add this to your tips: Do not plug or unplugged a PS/2 keyboard or mouse when the computer is on.

I'm assuming that the fuse is in the power supply but rather that taking it apart, I plugged in a new PS long enough to be able to get into the BIOS and changed the USB setting to enable legacy. But while I had the computer open, I noticed a jumper for enabling the keyboard wake up. Just for the heck of it, I changed the jumper and the PS2 keyboard now works without replacing the fuse. Edited April 4, 2009 by lewmur

[zlim]

WOW, lewmur fixes the impossible!I wouldn't know a jumper for enabling the keyboard wake up if I fell over it!

[striker]

Way to go Lew!

[tommyj12]

I don't know why usb keyboard isn't enabled by default in the bios on even the newest motherboards. I have to keep an old ps2 keyboard laying around for just this reason.

[lewmur]

WOW, lewmur fixes the impossible!I wouldn't know a jumper for enabling the keyboard wake up if I fell over it!

If there is a jumper within a 1/2" of the keyboard/mouse sockets, you can bet good money that's its function.

[V.T. Eric Layton]

I wouldn't know a jumper for enabling the keyboard wake up if I fell over it!

Here, Liz... I found a graphic representation of a jumper for you. Now you'll be able to recognize one when you next see one.

[Tushman]

Liz,Add this to your tips: Do not plug or unplugged a PS/2 keyboard or mouse when the computer is on.

Huh??? Doesn't make any bit of sense to me. In all the years I've been tinkering with computers, I've never once had any complications arising from doing so. Edited April 6, 2009 by Tushman

[striker]

I think it's a general rule of thumb to be on the safe side. I actually killed one MB way back years ago doing the plug out/plug in circus for a dead keyboard... Fortunately it was an experimenters MB not for production systems and I had a couple of other computers at hand. But it was then I learned this same lesson.For clarity: we're talking about PS/2, not USB.

[Tushman]

I think it's a general rule of thumb to be on the safe side. I actually killed one MB way back years ago doing the plug out/plug in circus for a dead keyboard... Fortunately it was an experimenters MB not for production systems and I had a couple of other computers at hand. But it was then I learned this same lesson.For clarity: we're talking about PS/2, not USB.

Yes I do realize you guys were talking about PS2 ports and not USB - hence my surprise. I have serviced between 1500-1700 computers during my career as a tech and have never once experienced any ill effects from unplugging a PS2 mouse while the system turned on. Perhaps I'm lucky?? I don't possess an electrical engineering degree either, so I still don't understand how the measely voltage from a PS2 connection could even damage a motherboard. Maybe if someone could give me a technical explanation I could begin to believe it.

[goretsky]

Hello,I do not think PS/2 ports are built surge suppression, so perhaps the damage is due to static electricity.Regards,Aryeh Goretsky

[b2cm]

Vcc/Ground provide power to the keyboard/mouse. The keyboard or mouse should not draw more than 275 mA from the host and care must be taken to avoid transient surges. Such surges can be caused by "hot-plugging" a keyboard/mouse (ie, connect/disconnect the device while the computer's power is on.) Older motherboards had a surface-mounted fuse protecting the keyboard and mouse ports. When this fuse blew, the motherboard was useless to the consumer, and non-fixable to the average technician. Most newer motherboards use auto-reset "Poly" fuses that go a long way to remedy this problem. However, this is not a standard and there's still plenty of older motherboards in use. Therefore, I recommend against hot-plugging a PS/2 mouse or keyboard.

http://www.computer-engineering.org/ps2protocol/

PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable. Hot swapping PS/2 devices usually does not cause damage due to the fact that more modern microcontrollers tend to have more robust I/O lines built into them which are harder to damage than those of older controllers; however, hot swapping can still potentially cause damage on older machines, or machines with less robust port implementations.

http://en.wikipedia.org/wiki/PS/2_connector