Cap replacement on a GA-8KNXP motherboard

[super64]

Hey guys, first time poster - also first time attempting to recap a motherboard!

I've had a good read through the forums but just want to make sure that I am making sensible choices for replacement caps for this Gigabyte 8KNXP motherboard.

Background: I picked up the machine this motherboard belonged to Facebook marketplace, so its history is unknown. By the looks of it, this machine probably stopped working at some point because the original PSU was replaced (PSU in it has modern plugs that didn't exist when this machine was new - 8pin and 24pin connectors were the giveaway).

I haven't tried powering this machine on because I wanted to do a full inspection first. As you can see from the attached images, the state of the KZG caps suggest it might not have worked anyway. The caps on the DPS module are slightly bulged but figured they should be replaced anyway.

I tracked down a schematic and I believe the KZG 3300uf 6.3v caps (10x25mm) are for vcore and the 1500uf 16v cap (10x20mm) is for 12v in.

I have found some Panasonic caps I thought might be a suitable replacement:

3300uf - https://au.rs-online.com/web/p/alumi...citors/7660044
1500uf - https://au.rs-online.com/web/p/alumi...citors/7083651

I'm just looking for guidance around whether the ESR, ripple and impedance of these caps will be OK.

Cheers!

[Uranium-235]

Re: Cap replacement on a GA-8KNXP motherboard

Look at the cap model, look it's ESR and ripple, and find a matching quality one with same or better specs. Long as it's the same type (low esr, ripple for motherboards), it should be fine. KZG is a pretty known suspect

I actually have this same motherboard in storage. I think it still works

[super64]

Re: Cap replacement on a GA-8KNXP motherboard

Thanks for getting back to me. The first computer I built was with this motherboard so getting it to work is more sentimental than anything.

I've found the datasheets and from what I gather, the KZG caps have the following rating:

- 3300uf 6.3v - Impedance is 0.012Ω and rated ripple is 2800mA
- 1500uf 16v - Impedance is 0.013Ω and rated ripple is 2550mA

The Panasonics that I linked are:

- 3300uf 6.3v - Impedance is 00.018Ω and rated ripple is 2470mA
- 1500uf 16v - Impedance is 0.020Ω and rated ripple is 2180Ma

I take it that Panasonic caps I chose are suboptimal. The problem is I can't seem to find any that match the KZG caps in stock anywhere - a problem I’m sure lots of people are experiencing at the moment.

I've found some Nichicon caps with better specs (out of stock at the moment) - 0.017Ω and ripple is 2900mA for the 3300uf cap. I assume this would be more suitable?

This is probably a silly question - how important is it to have impedance and ripple the same as the original?

[Uranium-235]

Re: Cap replacement on a GA-8KNXP motherboard

Thanks for getting back to me. The first computer I built was with this motherboard so getting it to work is more sentimental than anything.

I've found the datasheets and from what I gather, the KZG caps have the following rating:

- 3300uf 6.3v - Impedance is 0.012Ω and rated ripple is 2800mA
- 1500uf 16v - Impedance is 0.013Ω and rated ripple is 2550mA

The Panasonics that I linked are:

- 3300uf 6.3v - Impedance is 00.018Ω and rated ripple is 2470mA
- 1500uf 16v - Impedance is 0.020Ω and rated ripple is 2180Ma

I take it that Panasonic caps I chose are suboptimal. The problem is I can't seem to find any that match the KZG caps in stock anywhere - a problem I'm sure lots of people are experiencing at the moment.

I've found some Nichicon caps with better specs (out of stock at the moment) - 0.017Ω and ripple is 2900mA for the 3300uf cap. I assume this would be more suitable?

This is probably a silly question - how important is it to have impedance and ripple the same as the original?

Not important at those values. It's probably better to have a slightly higher ripple and lower impedance, but they're close enough you'll be fine. Besides, KZG is lower quality enough those values are probably smudged

[Per Hansson]

Re: Cap replacement on a GA-8KNXP motherboard

Those will be more than good enough, you have made good choices.
The only way to reach parity or better is with solid polymer capacitors.
But they are more expensive.

[RJARRRPCGP]

Re: Cap replacement on a GA-8KNXP motherboard

Hey guys, first time poster - also first time attempting to recap a motherboard!

I've had a good read through the forums but just want to make sure that I am making sensible choices for replacement caps for this Gigabyte 8KNXP motherboard.

Background: I picked up the machine this motherboard belonged to Facebook marketplace, so its history is unknown. By the looks of it, this machine probably stopped working at some point because the original PSU was replaced (PSU in it has modern plugs that didn't exist when this machine was new - 8pin and 24pin connectors were the giveaway).

I haven't tried powering this machine on because I wanted to do a full inspection first. As you can see from the attached images, the state of the KZG caps suggest it might not have worked anyway. The caps on the DPS module are slightly bulged but figured they should be replaced anyway.

I tracked down a schematic and I believe the KZG 3300uf 6.3v caps (10x25mm) are for vcore and the 1500uf 16v cap (10x20mm) is for 12v in.

I have found some Panasonic caps I thought might be a suitable replacement:

3300uf - https://au.rs-online.com/web/p/alumi...citors/7660044
1500uf - https://au.rs-online.com/web/p/alumi...citors/7083651

I'm just looking for guidance around whether the ESR, ripple and impedance of these caps will be OK.

Cheers!

Pentium 4 motherboards, usually run the Vcore from +12V, not +5V, unlike socket 462 and socket 370. I was thinking that 3300uF 6.3V caps were mainly on socket 462 and socket 370 motherboards. The 6.3V-rated caps are for +5V, I bet.

[Per Hansson]

Re: Cap replacement on a GA-8KNXP motherboard

That's a Pentium 4 board that supports up to Prescott 3.4Ghz according to Gigabytes website so I would say the CPU is VRM definitely running from +12v
And then the 3300uF 6.3v caps supply the processor VCore at around 1.2 to 1.4v
This is also confirmed by the schematic posted in the OP.

[RJARRRPCGP]

Re: Cap replacement on a GA-8KNXP motherboard

That's a Pentium 4 board that supports up to Prescott 3.4Ghz according to Gigabytes website so I would say the CPU is VRM definitely running from +12v
And then the 3300uF 6.3v caps supply the processor VCore at around 1.2 to 1.4v
This is also confirmed by the schematic posted in the OP.

So those caps are after the +12 volt is dropped down, but before the final stages. But, on that schematic, looks like 6.3V-rated caps are indeed used for the Vcore output.

[RJARRRPCGP]

Re: Cap replacement on a GA-8KNXP motherboard

That's a Pentium 4 board that supports up to Prescott 3.4Ghz according to Gigabytes website so I would say the CPU is VRM definitely running from +12v
And then the 3300uF 6.3v caps supply the processor VCore at around 1.2 to 1.4v
This is also confirmed by the schematic posted in the OP.

I guess this means that 6.3V is the usual lowest voltage rating and thus, you just go ahead and use 6.3V-rated caps for a rail as low as 1V.

[super64]

Re: Cap replacement on a GA-8KNXP motherboard

Those will be more than good enough, you have made good choices.
The only way to reach parity or better is with solid polymer capacitors.
But they are more expensive.

Thanks for the guidance Per, and thanks to everyone else for assisting!

I've gone ahead and ordered the Panasonics and will let everyone know how I go.

Cheers

[Uranium-235]

Re: Cap replacement on a GA-8KNXP motherboard

Thanks for the guidance Per, and thanks to everyone else for assisting!

I've gone ahead and ordered the Panasonics and will let everyone know how I go.

Cheers

Also, polymers usually can't reach that high capacitance. For 16V most of them reach 1500uf. Now that usually dosn't have much effect as the ESR and ripple is what matters. But this board seems a bit different especially with the separate VRM. Wouldn't recommend it