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

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:

If you need more information let me know

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.

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.

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.

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.

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.

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.

Congrats ! Maybe I should send you my CUV4X-ME so that you can repeat the fix ? 😉

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.

Same problem here on the original version of the cuv4x, followed the step of removing the c151 and everything was back to normal 😁

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.

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.

Hi, just to give feedback as my problem, similar but different. My MB is Asus CUV4X Rev 1.02, before I can do 2 or 3 strokes at the keyboard, being it PS/2 or USB. Everyone I see here says USB Keyboard works, mine have the exact same problem as PS/2, no difference.
Just removed the C151 IC with some flux and soldering iron, remove the excess solder and is working perfectly being it USB or PS/2, I have both connect as I'm installing Windows XP right now.

PARKE wrote on 2019-08-04, 12:46:

The original tip (which I cannot find anymore on the web) reads like this: […]
Show full quote

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.

This seems to have done the trick for me.
I used a stanley knife to cut the solder on the side facing the capacitor, not the PS2 ports.
The with a very small flat head from a screwdriver, I manage to pry it off.

It seems to have worked immediately. My keyboard started to be detected through the usb4vc device I use. Previously it was a lot hit and miss and sometimes I would even get stuck on POST without keyboard being detected. Now I even managed to get my MX Keys wireless detected using the usb4vc.
This board is an infinite source of knowledge.

elfoam wrote on 2021-10-12, 22:01:

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.

how stable without cap is it ? still have my old PC with ga-7vt600 1394 board that encountered this issue almost 8 years ago. it started to freeze and restart due to bad graphic card capacitors, and then BIOS checksum error etc. when it required to press F1 to continue keyboard no longer worked.

now i replaced caps on ATI card and i do get image of BIOS post screen but no reactions to keyboard. was already kinda preparing to do the BIOS mod and set USB keyboard to enabled as default, before i decided to have a look around the web one more time and found this thread

in this gigabyte board there are two black 8 leg components, but they are not capacitors like on other boards this fix was reported to work with, they are resistor networks and were not faulty.
however, there is a capacitor network too, i took it off, resistance on the line returned to normal and the keyboard is working.
it is a 4 line cap so CLK and DATA lines for each of the two ports which makes it simple to diagnose - CLK line on keyboard port was causing problems

Hi ive asus cusl2-c mobo which ps2 port not work. but cant find c151 on board anyone know where is it on mobo

There is a hd image of mobo here;

https://theretroweb.com/motherboards/s/asus-cusl2-c

I also removed the C151 from my ASUS CUBX rev 1.02 and the PS2 ports are working as they should.

Initially they were flaky and I had problems even with an USB to PS2 adapter. I had all sorts of problems ranging from the mouse pointer moving slowly to freezing, the keyboard taking seconds to register a key and other similar symptoms.

I wanted to test the cap but as it was removed with a solder blob it lost its legs. The board was not affected. I isolated the area with aluminum tape, then I applied some flux and with a solder blob I removed it safely. While it was in the board I measured the resistance and on the far side of it, the one towards the top edge of the board, I registered a different reading then the other three. This might be not relevant because probably it was connected to other things on the board.

I'll test the board for a week and I'll get back with the results but things are good so far.

One week later and after using the motherboard extensively I had no more problems with any of the PS2 ports. 😀