VOGONS


First post, by Justin1091

User metadata
Rank Member
Rank
Member

Hi guys,

Since some time my pc has keyboard errors. Connection dropping for a minute and then reconnecting without issues first, but now I can hear the pc speaker beeping when it's plugged in. It works for a couple of seconds, disconnects for a minute, works again etc.

The ps/2 port looks worn out, just like the mouse ps/2 port but that one works fine. I can see the keyboard LEDs (num-lock, etc) blink when powering on the pc, but still it will give a keyboard not connected error or it will boot but with an unusable keyboard. Last week when it still worked I could play a game for an hour and it would suddenly display the disconnecting behavior, and that wasn't because I pushed the PC case or touched the keyboard cable.

What gives? I can order a new 2 port PS/2 socket and solder that in, but if there's something else I can check I'd prefer to not desolder anything. I've had this board for ~10 years and it never had these issues, they started a couple of months ago but have now gotten so worse that I can't use a keyboard anymore on the PC. Motherboard is Asus CUV4-X by the way.

  • Tested USB keyboard - fine.
    Tested three PS/2 keyboards - all bad.
    PC beeps as if you press too many buttons when PS/2 keyboard is plugged in
    Issue occurs everywhere (bios, dos, 98se, 2K)
    Tried cleaning the port with contact cleaner
    Removed IO shield to be able to push the keyboard connector further in

Nothing worked so far, any suggestions are appreciated!

Reply 1 of 12, by treeman

User metadata
Rank Oldbie
Rank
Oldbie

sounds like a trace(s) from the keyboard plug on the motherboard might be failing/corroding. Sounds like typical symptom of a leaking barrel battery which is usually located around the keyboard plug and leaks around the area damaging traces around the area. A picture of your motherboard and close up of the area of the keyboard plug is needed

Just realised this is not from the barrell battery time, but a picture will help us get a better idea

Reply 2 of 12, by Justin1091

User metadata
Rank Member
Rank
Member
treeman wrote:

sounds like a trace(s) from the keyboard plug on the motherboard might be failing/corroding. Sounds like typical symptom of a leaking barrel battery which is usually located around the keyboard plug and leaks around the area damaging traces around the area. A picture of your motherboard and close up of the area of the keyboard plug is needed

Just realised this is not from the barrell battery time, but a picture will help us get a better idea

Sure. here are some pictures:

IMG-20190804-WA0000.jpg
Filename
IMG-20190804-WA0000.jpg
File size
115.8 KiB
Views
841 views
File comment
Outside port
File license
Fair use/fair dealing exception
IMG-20190804-WA0001.jpg
Filename
IMG-20190804-WA0001.jpg
File size
128.24 KiB
Views
841 views
File comment
Inside port
File license
Fair use/fair dealing exception
IMG-20190804-WA0002.jpg
Filename
IMG-20190804-WA0002.jpg
File size
169.43 KiB
Views
841 views
File comment
Backside pcb (top right is port location)
File license
Fair use/fair dealing exception
IMG-20190804-WA0004.jpg
Filename
IMG-20190804-WA0004.jpg
File size
362.42 KiB
Views
841 views
File comment
Area of ports
File license
Fair use/fair dealing exception

If you need more information let me know

Reply 3 of 12, by PARKE

User metadata
Rank Oldbie
Rank
Oldbie

The problem you describe is not uncommon on ASUS motherboards of that period.

https://www.badcaps.net/forum/printthread.php?t=829&pp=40
oooooooo
Quote:
After later look at ASUS's NetQ Forum found that the problem in Asus motherboards in certain types or the more common, these motherboards models include CUSL2, CUSL2-C, CUSL2-M, CUSL2-C-BP, TUSL2-C, TUSL2-C, CUV4X, CUV4X-C, CUBX, A7VPRO, etc., with the motherboard model and also having this problem
oooooooo

The fix that is described, removing chip c151, seems to work in some cases.

keyboard.jpg
Filename
keyboard.jpg
File size
611.63 KiB
Views
819 views
File license
Fair use/fair dealing exception

This fix did however not work on my own CUV4X-ME which had the same keyboard problem and, sadly, that board had to be retired after the operation.

Reply 4 of 12, by Justin1091

User metadata
Rank Member
Rank
Member
PARKE wrote:
The problem you describe is not uncommon on ASUS motherboards of that period. […]
Show full quote

The problem you describe is not uncommon on ASUS motherboards of that period.

https://www.badcaps.net/forum/printthread.php?t=829&pp=40
oooooooo
Quote:
After later look at ASUS's NetQ Forum found that the problem in Asus motherboards in certain types or the more common, these motherboards models include CUSL2, CUSL2-C, CUSL2-M, CUSL2-C-BP, TUSL2-C, TUSL2-C, CUV4X, CUV4X-C, CUBX, A7VPRO, etc., with the motherboard model and also having this problem
oooooooo

The fix that is described, removing chip c151, seems to work in some cases.

keyboard.jpg

This fix did however not work on my own CUV4X-ME which had the same keyboard problem and, sadly, that board had to be retired after the operation.

Interesting! Never expected something like that. Unfortunately I don't have a soldering iron atm, but when I get one I'll remove it. Would it be better to replace it with a new component? What is it anyway, a capacitor?

Keyboard is now working again for now.. actually typing this post using the ps/2 port. It'll probably disconnect again in a bit. If it's indeed the c151 chip then it must have failed last month because I never had these issues before. It also doesn't affect the mouse ps/2 port because that always works.
Thanks a lot for this information. I'll post back here when I've removed the component, but that will probably take a while as I need to buy a new soldering iron.

Reply 5 of 12, by PARKE

User metadata
Rank Oldbie
Rank
Oldbie

The original tip (which I cannot find anymore on the web) reads like this:

ooooooooooooooooooooooooooooooooooooooooo
puzzleman
VIP Member
Posts : 11063
Level :
Tech Points : 79
From: CHN
Posted:4/20/2007 4:01:00 PM # 2

The board is out of 3 years warranty.
I tell you a way to try:
Please take the motherboard out of case,
then check the board.
there should be a 8 legs capacitor lies behind the PS2 port,
it is marked with " C151 " on its surface.
Please remove it from motherboard by force.
then try to test with PS2 functions.
ooooooooooooooooooooooooooooooooooooooooo

What I did was, I carefully cut the c151 solder on one side with a small Stanley knife and after some wriggling it came loose. But the problem was not solved so the board ended up in a box (I don't like flawed boards in cases as long as there are still fully functional boards around).
I suspect that when the problem has been consistent over a longer period and there have been a number of disconnects-reconnects while the board is running (in other words hot plugging) that the I/O gets damaged beyond repair. But that is guesswork on my part.

Reply 6 of 12, by gdjacobs

User metadata
Rank l33t++
Rank
l33t++
Justin1091 wrote:

Interesting! Never expected something like that. Unfortunately I don't have a soldering iron atm, but when I get one I'll remove it. Would it be better to replace it with a new component? What is it anyway, a capacitor?

Keyboard is now working again for now.. actually typing this post using the ps/2 port. It'll probably disconnect again in a bit. If it's indeed the c151 chip then it must have failed last month because I never had these issues before. It also doesn't affect the mouse ps/2 port because that always works.
Thanks a lot for this information. I'll post back here when I've removed the component, but that will probably take a while as I need to buy a new soldering iron.

You can check if the array is failed short anywhere (common enough with MLCC caps) with an impedance check on a multimeter. The plate contacts oppose each other across the width of the array, like a set of SMT caps lined up.

All hail the Great Capacitor Brand Finder

Reply 7 of 12, by Justin1091

User metadata
Rank Member
Rank
Member

So after soaking the ps/2 port and the area around it multiple times in alcohol last week, it's fully functional. First I poured it in the ps/2 connector and dried it with compressed air, this didn't work. Then I poured it around the c151 and let it stay there until it dried: keyboard works again.

Maybe it'll go bad again, but for now it's fine. Been using the pc for days without issues.

Reply 9 of 12, by Justin1091

User metadata
Rank Member
Rank
Member

So after a month of using the PC and the keyboard without issues, it failed again yesterday. This time I couldn't even get past the keyboard error at POST.

Decided to take out the C151.. problem solved! I wonder how it gets bad over time and whether I should replace it. What do you guys think? They put it there for a reason obviously.

Reply 11 of 12, by wiretap

User metadata
Rank Oldbie
Rank
Oldbie
Justin1091 wrote on 2019-09-13, 18:53:

So after a month of using the PC and the keyboard without issues, it failed again yesterday. This time I couldn't even get past the keyboard error at POST.

Decided to take out the C151.. problem solved! I wonder how it gets bad over time and whether I should replace it. What do you guys think? They put it there for a reason obviously.

It can be replaced. It is a 4 element capacitor array, 0612 size, 150pF.
https://www.mouser.com/ProductDetail/Yageo/CA … fOWXyUeiw%3D%3D

They are kind of an odd component to solder -- I've done a few of them in the same package/size on other PCB projects. The keyboard connector may need to be removed if using a soldering iron. Otherwise, hot air with a tiny amount of solder paste on the pads may work better.

Yes, it is there for a reason, but without schematics,it would be hard to determine why. Looks like keyboard input signal decoupling/filtering.

Circuit Board Repair Manuals
My Project List

Reply 12 of 12, by elfoam

User metadata
Rank Newbie
Rank
Newbie

You guys are complete legends ! The capacitor array on my Gigabyte GA-6OXM7E is a different value but in the same location right behind the PS2 port. I had already replaced the Super IO controller but in the end removing the capacitor array fixed it. Decide to add this post for whoever searches this up in the future with the Gigabyte board.