Check continuity across that green "P110" SMD. It's a fuse. Perhaps they wanted to bypass it to allow more current to something. Maybe it was done that way after it blew and never reset. The PS/2 port looks barely soldered in there, almost like you could yank it out. Maybe some other kind of mini-din connector (they're prevalent enough) got plugged in which didn't belong there. "It's got S-Video!" So the jack was probably replaced.

I also see "FUSE2" silk screened near the COM1 label. Check and see if that one is not open as well.

Auzner wrote:

Check continuity across that green "P110" SMD. It's a fuse. Perhaps they wanted to bypass it to allow more current to something. Maybe it was done that way after it blew and never reset. The PS/2 port looks barely soldered in there, almost like you could yank it out. Maybe some other kind of mini-din connector (they're prevalent enough) got plugged in which didn't belong there. "It's got S-Video!" So the jack was probably replaced.

I also see "FUSE2" silk screened near the COM1 label. Check and see if that one is not open as well.

Thanks for the fast tip!

Fuse1 (P 110) and Fuse2 (the small white rectanglular bit?) both are open when I do a continuity test. There is also continuity between the fuses and the +5v pin in the mouse port (figured it was worth it to test that too).

I actually took the rest of the pieces off of the PS/2 port since the remaining sleeve wasn't even soldered on (as you mentioned). All of the pins inside look fine. This is the first time I've ever seen the inside of a PS/2 port. They certainly don't look the way I'd expected. Its interesting to think that you can probably swap the different colored ports from other boards since the plastic casings slide free from the pins and hook together like puzzle pieces.

Anyway... I wish I had more knowledge of circuits. I'm sure I could follow these to some point where it would either reveal if there was a problem or not.

Yeah, I think it's that white one. An open circuit is a blown fuse, you want it to beep good, being continuous or closed.

Whoops, I meant closed, not open. Derp. 😵

So, I figured I'd never know what exactly was going on with that wire in place, so I just tugged on it a little and it came loose easily. :p

EDIT: I was misreading something. I'll keep investigating this before posting any more wrong stuff. 🤣

When I check resistance between the +5v pin on the PS/2 connector and the +5v on the ATX socket, it showed some resistance but it kind of bounces around between 3.5 and 1.8 Kohm. Seems to be connected? I think I can probably try it this way without the wire in place, and see what's going on.

Ozzuneoj wrote:

When I check resistance between the +5v pin on the PS/2 connector and the +5v on the ATX socket, it showed some resistance but it kind of bounces around between 3.5 and 1.8 Kohm. Seems to be connected? I think I can probably try it this way without the wire in place, and see what's going on.

Diode drop, maybe?

Looks like some sort of fix of the PS/2 ports. Maybe there was physical damage and they replaced the ports? Looks like they were resoldered on (not very well as you and others also noticed).

I assume you checked, but the way the wire is attached to the board it's bare wires are (almost?) touching other solder points.

The wire was close to touching one other solder point but it was also a +5v. I have removed the wire since there does seem to be some connection to the +5v on the PS2 ports without it. I powered up the board with no CPU and it didn't catch on fire, so I installed the CPU and tried it. The system seems to work fine with a USB keyboard but I cannot get a PS/2 keyboard to work (not sure about PS/2 mouse yet as I don't have an OS installed).

I have a bad feeling that something worse than a single SMD component is at fault here. Where would the keyboard controller be on a KX133 board? I'm assuming it'd be in the chipset, not some separate component.

Reading online I'm seeing a few complaints of bad PS/2 ports from this era, and one from this same board.

Anyway, here's a picture to show why I care about fixing this...

Using a USB keyboard seems to work for most things, including DOS, but if there's an issue with a USB driver in Windows 98 I'm kind of stuck. It seems like the PS/2 mouse port is also dead. Anyone have experience diagnosing problems like this? It doesn't really seem like a power issue, it seems more likely that they tried to run the +5v and it didn't work so they never bothered putting it all back together.

Ozzuneoj wrote:

The wire was close to touching one other solder point but it was also a +5v. I have removed the wire since there does seem to be […]
Show full quote

The wire was close to touching one other solder point but it was also a +5v. I have removed the wire since there does seem to be some connection to the +5v on the PS2 ports without it. I powered up the board with no CPU and it didn't catch on fire, so I installed the CPU and tried it. The system seems to work fine with a USB keyboard but I cannot get a PS/2 keyboard to work (not sure about PS/2 mouse yet as I don't have an OS installed).

I have a bad feeling that something worse than a single SMD component is at fault here. Where would the keyboard controller be on a KX133 board? I'm assuming it'd be in the chipset, not some separate component.

Reading online I'm seeing a few complaints of bad PS/2 ports from this era, and one from this same board.

Anyway, here's a picture to show why I care about fixing this...

<snip>

Using a USB keyboard seems to work for most things, including DOS, but if there's an issue with a USB driver in Windows 98 I'm kind of stuck. It seems like the PS/2 mouse port is also dead. Anyone have experience diagnosing problems like this? It doesn't really seem like a power issue, it seems more likely that they tried to run the +5v and it didn't work so they never bothered putting it all back together.

I have read about PS/2 problems like these here on Vogons before, but I have never seen a fix unfortunately. Abit 440BX boards seem vulnerable to this.

Good luck with it. That CPU deserves a good board. Send it to me if you can't get it to work (ha ha). 😀

Okay, here we are with an 8-year follow up. Yeesh... 🤣

I have been on a board repair frenzy this week and this board came up, so I decided to take a stab at it with an additional 8 years of experience, new tools and with new information.

Since the last post in this thread I have seen several posts about the dead ASUS PS/2 port issue being caused by the notorious CN1 (C151) capacitor array going bad, and that simply removing it will fix the problem. I finally had the chance to do this (since the K7V has the same component in that location) and, sadly, I still have no PS/2 keyboard detected. I also replaced the entire PS/2 port assembly since I had one laying around... still nothing.

So, with CN1 removed and a different set of ports installed, I am now even more suspicious of the bodge wire that was on this board when I got it. It seems logical that this capacitor array was bad and caused the ports to stop working, but the original owner did not realize this so they did some weird thing with a bodge wire trying to get the ports working again.

I am curious as to what could have been damaged by the 5v from the USB port being run directly to the 5v pin on the PS/2 port.

I will try to poke around but if anyone has any ideas in the meantime, let me know.

https://www.chinafix.tech/asus-motherboard-k7 … 1-01-boardview/
check l1 ferrite bead

shevalier wrote on 2026-02-08, 06:28:

https://www.chinafix.tech/asus-motherboard-k7 … 1-01-boardview/
check l1 ferrite bead

Okay, that might be it!

I just tested L1 and I'm definitely getting more resistance than expected... anywhere from 4ohms to 16ohms. Those readings might just be the resistance of some other path through the circuit if the ferrite is open circuit.

When I get some time tomorrow afternoon I will replace that and see if that does it.

Thank you!

EDIT: Also, I just looked at the board to find L1. I wasn't able to do anything with the schematics on that site... the account registration process seems broken. I can download the zip with all of the files, but what do I with them?

Ozzuneoj wrote on 2026-02-08, 06:42:

Okay, that might be it! […]
Show full quote

shevalier wrote on 2026-02-08, 06:28:

https://www.chinafix.tech/asus-motherboard-k7 … 1-01-boardview/
check l1 ferrite bead

Okay, that might be it!

I just tested L1 and I'm definitely getting more resistance than expected... anywhere from 4ohms to 16ohms. Those readings might just be the resistance of some other path through the circuit if the ferrite is open circuit.

When I get some time tomorrow afternoon I will replace that and see if that does it.

Thank you!

EDIT: Also, I just looked at the board to find L1. I wasn't able to do anything with the schematics on that site... the account registration process seems broken. I can download the zip with all of the files, but what do I with them?

http://boardviewer.net/
Download the viewer, open Format.asc with it.
And voilà, PCB is right in front of you.

shevalier wrote on 2026-02-08, 07:26:

http://boardviewer.net/ Download the viewer, open Format.asc with it. And voilà, PCB is right in front of you. […]
Show full quote

Ozzuneoj wrote on 2026-02-08, 06:42:

Okay, that might be it! […]
Show full quote

shevalier wrote on 2026-02-08, 06:28:

https://www.chinafix.tech/asus-motherboard-k7 … 1-01-boardview/
check l1 ferrite bead

Okay, that might be it!

I just tested L1 and I'm definitely getting more resistance than expected... anywhere from 4ohms to 16ohms. Those readings might just be the resistance of some other path through the circuit if the ferrite is open circuit.

When I get some time tomorrow afternoon I will replace that and see if that does it.

Thank you!

EDIT: Also, I just looked at the board to find L1. I wasn't able to do anything with the schematics on that site... the account registration process seems broken. I can download the zip with all of the files, but what do I with them?

http://boardviewer.net/
Download the viewer, open Format.asc with it.
And voilà, PCB is right in front of you.

Ah, okay! Thanks. I see now that the page says "Boardviewer" right on it... which makes sense, heh. To be honest, I ran right over to my board to test L1 when I read your message and didn't look too closely at that site. 😅

I will download it now though. Looks very handy.

Ozzuneoj wrote on 2026-02-08, 08:17:

Looks very handy.

Only for repair technicians.
Who carry out work according to manuals - ‘if A doesn't work, check part 1, part 2, part 3’.
If the motherboard is glitching or has schematic issues, working with BoardViewer is painful; schematics are much better.
But it's much better than nothing in any case.

shevalier wrote on 2026-02-08, 06:28:

https://www.chinafix.tech/asus-motherboard-k7 … 1-01-boardview/
check l1 ferrite bead

I should have thought of this earlier, but I have no idea what to use to replace this. I have all sorts of SMD components on hand including things that look like this that were scavenged from other boards over the years.

I have a package of SMD 1UH inductors of this size, but I don't think that serves the same purpose.

The bill of materials says L1 is this:
FERRITE BEAD SMD(1206) 3A 70 OHM/100MHZ A TYPE

Short of purchasing that specific item somewhere and paying to ship was is effectively one grain of sand, I'd love to just use something I have on hand if possible. Is there a way I can measure the components I have on hand to find a close-enough replacement for this? I have a DER DE-5000 LCR meter, but if I am understanding this correctly (I have zero experience with SMD ferrite beads) then this ferrite should measure 70 ohms at 100mHz... but my LCR meter is nowhere advanced enough for near that, since it tops out at 100kHz.

EDIT: My caveman electronics repair skills tell me that this is good enough, but I have no idea:
I tested the resistance of L6 and L32 (since they are the same component as L1 on the BOM) and they measure the same (~0.05ohms). L1 is way off compared to those (1+ ohms, it fluctuates). I found some identical looking ferrites in my pile of harvested components and a couple of them measure basically the same as L6 and L32 (~0.05ohms). What is the worst that could happen if I swap L1 out for one of these?

Well, I went for it. When I desoldered L1 with hot air, the end was actually broken off and wasn't connected to the rest of it, so it was definitely bad.

I put in one of the ferrites I had on hand that had a similar resistance to the others (which may be a meaningless measurement, I don't know) and it definitely did SOMETHING because the three lights on the keyboard now flash during POST, but I still get a no keyboard present error and it is non-functional. So, I'm guessing there is still at least one component in the chain that is bad. Or, is it possible that this is from using a close-but-not-quite-right ferrite at L1?

EDIT: I just tested CN1 which I had removed before and it seems to be okay? I am measuring around 150pf on each of the four sections of the capacitor array. I can try putting that back in, but considering the fact that ASUS themselves told people back in the day to literally bust the thing off with a sharp object once the board was out of warranty, I don't think it should be necessary and I would rather not risk it going bad later.

EDIT2: Oh! I think I've got it!

Now that I look through my microscope, I see that L13 and L14 are both cracked as well and they measure in the mega-ohm range, where as L15 and L16 are in the 0.05ohm range. Sure enough, Boardview tells me that these are directly connected to the LMSDATA and LKBDATA pins. That is why I am not getting anything despite the keyboard having power. So, assuming there is nothing else further down the line that is also damaged, swapping these out with some similar ferrites will hopefully fix this problem.

MAN, Boardview is incredibly helpful when you have a real schematic of the board you're working on... holy cow. I wish I had this for every board I own. It's a complete game changer having a schematic.

Yes! It's fixed! 🥳

I had some really undesirable and broken card laying here and I just stole some ferrites off of it that were the same size. The resistances I measured on them weren't an exact match of what came off of this board, but they are all well under 0.1ohm, so I figured it'd be worth a shot. I figured at worst it could make the input flaky, but it should at least tell me whether I have a deeper issue with the keyboard and mouse input.

I swapped them out pretty easily and I'm pleased to say that the keyboard and mouse ports are both working flawlessly now! I checked the ferrites with my thermal camera and nothing is heating up at all, so unless I start noticing issues with the input I am going to call this board fixed - FINALLY - after 8 years in my possession and likely close to 25 years since someone stuck that bodge wire on it to solve the keyboard problems.

This is a really nice board too. I updated the BIOS and I believe it should have Thunderbird support. The BIOS is also just jam packed with features and settings.

The first computer I built myself (my brother was showing me what to do, but we built it together) was a Tyan S2380 with a KX133 chipset and an Athlon 750Mhz, so this is very close to that. I'm sure functionally this doesn't do much that my Slot 1\ Socket 370 systems can't do, but it's a nice platform and it gives me that warm fuzzy feeling. 🙂

I'm very happy to finally have this board working again. I originally got it because it came with an absolute unicorn of a CPU installed... the original pre-Thunderbird Athlon 1Ghz, which is the first 1Ghz consumer CPU to hit the market. I'm not sure if I will reunite them or put that processor in a different Slot A board. At least I have options now though. 😁

Thank you so much shavelier for the advice and for connecting me with Boardview and the board schematics. Realistically, I would have found those broken inductors eventually because I obsess over stuff like this and would have stared at it through my microscope until I found something that looked off (which they did upon close inspection), but being directed to the ferrite beads and the full board schematic undoubtedly saved me many hours of diagnostics.

VOGONS does it again. 😀

Congratulations!
I don't usually bother with ferrite beads, there are only two types:
- power (high current, low impedance for alternating current)
- signal (the opposite)
If you need a power one, check the power circuits of the donor and remove any that are the right size.
If you need a signal one, these are the lines for the USB, keyboard, DVI/D-SUB.

As for the schematics, well, everything on the boards is so formulaic and uniform...
Now you will understand what keyboard layouts look like on almost any board. 😀
PS. There's a screw nearby, so either the screwdriver slipped, or they forgot to unscrew the screw and started removing the board. Cracks can easily occur.