Nobody has ideas eh? 😁

appiah4 wrote on 2026-07-31, 07:41:

I am troubleshooting a Chaintech CT-6VIA3. The board posts with no errors and after IDE detection throws errors about default cmos values being loaded and gets stuck. I can not get into the BIOS. It is a peculiar problem because the Keyboard does not seem to be working. The three lights flash upon boot, but after that it never seems to function. Pressing Caps Lock / Scroll Lock does not result in the led lighting up. I've replaced the battery and reseated the BIOS chip to no avail. The keyboard I am using is a generic HP PS/2 office keyboard that works with everything else I have. I tried a USB keyboard, but had no luck. I tried to see if shorting the keylock pins does anything, but it does not fix the issue (and adds a Keyboard locked error after IDE detection).

Interestingly enough I have video of the board actually proceeding to boot from the nice guy I got the board from, so unless something happened in the mail the board should not be faulty. I was wondering if anyone has any pointers as to what to look at? Help is welcome 😀

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those packages with four caps in one behind the ps2 connectors.
I've read that heating them up with a soldering iron might breath some more life into them but they'll eventually degrade again.
Me, I'm left to wonder which mainboard you're talking about since you linked to a pcchips board, while mentioning a chaintech board in the title ?

weedeewee wrote on 2026-08-02, 08:25:

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those p […]
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appiah4 wrote on 2026-07-31, 07:41:

I am troubleshooting a Chaintech CT-6VIA3. The board posts with no errors and after IDE detection throws errors about default cmos values being loaded and gets stuck. I can not get into the BIOS. It is a peculiar problem because the Keyboard does not seem to be working. The three lights flash upon boot, but after that it never seems to function. Pressing Caps Lock / Scroll Lock does not result in the led lighting up. I've replaced the battery and reseated the BIOS chip to no avail. The keyboard I am using is a generic HP PS/2 office keyboard that works with everything else I have. I tried a USB keyboard, but had no luck. I tried to see if shorting the keylock pins does anything, but it does not fix the issue (and adds a Keyboard locked error after IDE detection).

Interestingly enough I have video of the board actually proceeding to boot from the nice guy I got the board from, so unless something happened in the mail the board should not be faulty. I was wondering if anyone has any pointers as to what to look at? Help is welcome 😀

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those packages with four caps in one behind the ps2 connectors.
I've read that heating them up with a soldering iron might breath some more life into them but they'll eventually degrade again.
Me, I'm left to wonder which mainboard you're talking about since you linked to a pcchips board, while mentioning a chaintech board in the title ?

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3

There is one electrolytic and four smd inductors behind the ps2 port.

There is also an 8 legged smd component labelled C470 which I guess is what you refer to?

appiah4 wrote on 2026-08-02, 14:31:

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3 […]
Show full quote

weedeewee wrote on 2026-08-02, 08:25:

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those p […]
Show full quote

appiah4 wrote on 2026-07-31, 07:41:

I am troubleshooting a Chaintech CT-6VIA3. The board posts with no errors and after IDE detection throws errors about default cmos values being loaded and gets stuck. I can not get into the BIOS. It is a peculiar problem because the Keyboard does not seem to be working. The three lights flash upon boot, but after that it never seems to function. Pressing Caps Lock / Scroll Lock does not result in the led lighting up. I've replaced the battery and reseated the BIOS chip to no avail. The keyboard I am using is a generic HP PS/2 office keyboard that works with everything else I have. I tried a USB keyboard, but had no luck. I tried to see if shorting the keylock pins does anything, but it does not fix the issue (and adds a Keyboard locked error after IDE detection).

Interestingly enough I have video of the board actually proceeding to boot from the nice guy I got the board from, so unless something happened in the mail the board should not be faulty. I was wondering if anyone has any pointers as to what to look at? Help is welcome 😀

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those packages with four caps in one behind the ps2 connectors.
I've read that heating them up with a soldering iron might breath some more life into them but they'll eventually degrade again.
Me, I'm left to wonder which mainboard you're talking about since you linked to a pcchips board, while mentioning a chaintech board in the title ?

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3

There is one electrolytic and four smd inductors behind the ps2 port.

There is also an 8 legged smd component labelled C470 which I guess is what you refer to?

Yes.
If you search the forum for "shevalier capacitor keyboard", you'll find the posts i'm referring to.

Anyway, it's just a guess, it could be something totally different. Enjoy !

weedeewee wrote on 2026-08-02, 15:00:

Yes. If you search the forum for "shevalier capacitor keyboard", you'll find the posts i'm referring to. […]
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appiah4 wrote on 2026-08-02, 14:31:

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3 […]
Show full quote

weedeewee wrote on 2026-08-02, 08:25:

shevalier likes to go for a specific capacitor... I think he's been right about that several times on this forum. one of those packages with four caps in one behind the ps2 connectors.
I've read that heating them up with a soldering iron might breath some more life into them but they'll eventually degrade again.
Me, I'm left to wonder which mainboard you're talking about since you linked to a pcchips board, while mentioning a chaintech board in the title ?

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3

There is one electrolytic and four smd inductors behind the ps2 port.

There is also an 8 legged smd component labelled C470 which I guess is what you refer to?

Yes.
If you search the forum for "shevalier capacitor keyboard", you'll find the posts i'm referring to.

Anyway, it's just a guess, it could be something totally different. Enjoy !

I didn't come up with this solution myself. I also picked it up from one of the threads on this forum.

shevalier wrote on 2026-08-02, 16:18:

I didn't come up with this solution myself. I also picked it up from one of the threads on this forum. https://www.vogons.org/do […]
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weedeewee wrote on 2026-08-02, 15:00:

Yes. If you search the forum for "shevalier capacitor keyboard", you'll find the posts i'm referring to. […]
Show full quote

appiah4 wrote on 2026-08-02, 14:31:

My bad, the link is: https://theretroweb.com/motherboards/s/chaintech-ct-6via3

There is one electrolytic and four smd inductors behind the ps2 port.

There is also an 8 legged smd component labelled C470 which I guess is what you refer to?

Yes.
If you search the forum for "shevalier capacitor keyboard", you'll find the posts i'm referring to.

Anyway, it's just a guess, it could be something totally different. Enjoy !

I didn't come up with this solution myself. I also picked it up from one of the threads on this forum.

Thank you, very useful. As far as I can understand that capacitor network serves no purpose, and removing it would be completely safe and likely fix the issue? This is what I will try.

Afaik its for EMI suppression and ESD. Might have died from ESD too doing its job.
Sounds like KBC must be seeing keyboard just fine if its not complaining. Does the board complain with keyboard unplugged?

similar case Strange PS/2 KB/mouse problem on QDI Advance 5/133E (VT82C693A + VT82C596B)

appiah4 wrote on 2026-08-02, 20:20:

it would be completely safe

This is part of some port protection against noise/interference induced on the cables between devices.
It's better to replace it with a 100-470pF C0G/NP0 capacitor array.

rasz_pl wrote on 2026-08-03, 02:37:

Afaik its for EMI suppression

Only a very clunky one.
But that's how it was done in the reference design, and no one bothered to redesign it because the price was acceptable to everyone.
Back then, it was trendy to stuff ferrite beads everywhere.
The best option would be a symmetrical T-filter consisting of two $100\,\Omega$ resistor arrays and a $100\text{--}470\,\text{pF}$ capacitor array.
This would be comparable in both cost and footprint, but the resistors would limit the current through the capacitors.
But copy-paste is just so copy-paste. Beyond that, nobody even bothered to use their head.