Identifying reason for board's similar caps, but different physical sizes

[Masejoer]

I have this board which converts 19V to PC Voltages:




The green and purple capacitors have the same Voltage, capacitance, and temperature ratings. The purple caps are smaller than the blue-green (more greenish in person).





The blue-green caps are used on the 12V section:




I can't find anything online about these capacitors. Is there any reason the 12V section would be using different capacitors, when the primary specs are identical?

Just need to see if I can use the Nichicon 1000uF 25V VZ or Nichicon 1500uF 16V HN caps that I have here for them all, or if I need to be more selective for the 12V section.

[budm]

I can see that the purple one is the FZ series, but I cannot see what the others are in the pictures.

[Masejoer]

Originally Posted by budm

I can see that the purple one is the FZ series, but I cannot see what the others are in the pictures.

The others don't say anything more than what I took photos of.

I went and replaced all the caps with my Nichicons and the system is working again. I didn't differentiate between the two different 1000uF.

Still curious what the difference could be though, being that the only difference is that the blue-green ones were on the 12v circuit.

[stj]

different ripple current handling, and/or lifespan.

[Hitto]

Originally Posted by Masejoer

I can't find anything online about these capacitors. Is there any reason the 12V section would be using different capacitors, when the primary specs are identical?

The producer using capacitors of lower specs where permissible ripple in that path allowed for a cheaper component without any immediate drawback. Which translates in the minimum necessary component count for the whole circuit to work.

The reason is no more nor less than the art of cost cutting.

[Masejoer]

Thanks - I will continue to run it as-repaired with my Nichicons. My NAS has been down since October, relying only on manual backups since then. The automated full backup started this morning is running great.

[redwire]

The power supply is a over-rated, those buck output capacitors are all undersized for the PCB ratings "5A" or "8A". I would be stuffing in the largest value parts I could fit, like 2,200uF each or polymer types.
Then there's a MC34063 there that made me chuckle. I'm saying the design is a bit wonky.

I have seen each capacitor chosen because that's what they have laying around, got a good deal on, or cost-optimized down to the penny- also considering product lifetime.
One giveaway is the 5V and 3.3V outputs are using 16V parts, a waste of space.

[Masejoer]

Originally Posted by redwire

The power supply is a over-rated, those buck output capacitors are all undersized for the PCB ratings "5A" or "8A". I would be stuffing in the largest value parts I could fit, like 2,200uF each or polymer types.
Then there's a MC34063 there that made me chuckle. I'm saying the design is a bit wonky.

I have seen each capacitor chosen because that's what they have laying around, got a good deal on, or cost-optimized down to the penny- also considering product lifetime.
One giveaway is the 5V and 3.3V outputs are using 16V parts, a waste of space.

Yeah, I don't want this nas setup much longer - I've outgrown it, but want to keep a compact, quiet, non-rackmount setup. I'm waiting for U-NAS products to come back in stock so I can swap up to an 8-bay with user-selectable psu, rather than external brick using 4-pin mini-DIN, and then this DC-DC board inside the case.

The board sits just under the backplane, so cap height is an issue in a couple spots. 16V 1500uF would fit in there.

[momaka]

Originally Posted by Masejoer

Just need to see if I can use the Nichicon 1000uF 25V VZ or Nichicon 1500uF 16V HN caps that I have here for them all, or if I need to be more selective for the 12V section.

That PSU converter board appears to use buck VRM circuits, so I suggest going with low ESR caps.

Thus, I suggest to use the Nichicon HN 16V 1500 uF caps, provided they weren't manufactured between 2001 and 2004 (they will have a date code that reads similar to "Hxxyy", where xx indicates the year, and yy the week or production - so for example, H0531 means made in the 31st week of 2005).

As for the VZ, those are general purpose 105C caps and so may not last too long on that buck converter circuit too long.

[pc7fan]

Sacon? Rebadged GSC, garbage caps. Glad the PSU is working after the repair.

[Uranium-235]

it's not voltages within PC range for ripple/esr, it's for a sata II backplane (which sata does have 3.3/5/12)

edit: scratch that, I got my model numbers confused on this PDF http://www.chenbro.com/en-global/Dow...e/download/219

but that uses an internal psu so that can 't be your product

[momaka]

Originally Posted by pc7fan

Sacon? Rebadged GSC, garbage caps. Glad the PSU is working after the repair.

Exactly!

Sacon is not actually re-badged GSC. It's the same company that makes them. They just changed names several times, because their caps are THAT BAD.

i.e. GSC = Evercon = Sacon
And I think their last name or at least a close associate was Elcon. All garbage caps, though. Just recap these as soon as you see them.

Here are some Sacon FZ I pulled from a graphics card a while back:
https://www.badcaps.net/forum/attach...1&d=1499527964
https://www.badcaps.net/forum/attach...1&d=1499527964
^ Yes - once they blow, they tend to dry themselves up quickly and only start showing picoFarads (pF) of capacity. If the circuit they are in can't handle it, you can get destroyed hardware. I obtained two EVGA GeForce 7600 PCI-E cards that was some years back. Miraculously, XFX cards seem to have better VRM design, because they almost never get destroyed from these crappy caps. I saved a good number of XFX GeForce 8600 and GeForce 6800 XT AGP cards now, among others.

Also, be careful - sometimes, those Sacon FZ caps will imitate polymers by not stamping vents on their cans:
https://www.badcaps.net/forum/showthread.php?t=37146l=
^ Unsurprisingly, they still managed to go bad... and nearly launch themselves out of the board. Such garbage!