Reply 20 of 49, by PCBONEZ
Of course from one line of caps to another, that term is rather relative...
Anything with an ESR (Impedance) less than 0.090 ohms @100kHz would be considered low ESR.
That is not an official standard but rather a rule of thumb used by old Electronics Techs like me.
Regarding Al-Lytic caps in the physical size range used for main power filtering on mobos and in PSUs.
.. meaning 6mm to 12.5mm diameter caps in typical lengths...
@100kHz ESR effectively = Impedance (It's within about 0.002 ohms @100kHz)
Exceptions are rare in that size range.
Outside that range it's still pretty close until you get far away in size.
Thus datasheets for mobo sizes of cap intended for 100kHz typically use the terms Impedance and ESR interchangeably.
You are speaking to the actual inventor of the technique used to compare ESR Grades.
I did it back during the Capacitor Plague while frequenting badcaps.net.
It's now used universally by techs in the caps repair industry but I never get credit for it because I did it openly on BCN instead of publishing it in a book or web page or something.
Most people that use it have no idea who created it.
Unfortunately I'm doing a file server upgrade and my comparison charts and tables have been offloaded to cold (shelved) hard drives. Can't readily access them. (And if I don't quit OCD'ing my favorite topics in forums it's going to be July before I finish the new file server.)
I will outline how it's done in another post. - Come to think I may have done that already on Vogons.
Wasn't recent. I don't remember for sure. Have to check. I might have posted some of my charts already.
The replacements I used were much higher quality and low impedance, but not from a series intended to be low ESR. (Panasonic KA and Nichicon UPW/UHE)
Oh boy did you screw up.
You used low ESR caps.
As described above Low Impedance effectively IS low ESR.
PW and HE are both low ESR grades.
PW are entry level but not the absolute bottom tier.
HE are few steps higher grade (lower ESR). Pretty close to the middle of the low ESR range.
PW is an exact grade match Panasonic FC. So much so that you can interchange the datasheets.
Intel used FC and PW in VRM on Intel SE440BX boards. I think that's what is on SE440BX-2 as well.
PW were common in final output filters in PSUs. I still see them occasionally in newer PSUs.
HE is an exact grade match Chemicon KY.
HE and KY saw use as VRM caps in socket 370 and as Field caps into socket 775/771.
KY were common in final output filters in PSUs. I still see them there in newer gear fairly often.
Both PW and KY are very common in final output of non-PC related PSUs and in better LCD screens.
KA were a bad choice because they are 85°C, not because their ESR is in the GP cap range.
The tiny caps on older boards do not need to be low ESR.
[IIRC] Those started becoming low ESR mid socket 478 era. Even then only sometimes,
Because the cost difference is nil it's common practice to use low ESR replacements if you have to replace those.
This also means you only need to stock one kind for that cap size/uF/volts, and its easier get the quantity discounts.
You might think the 85°C is not that important for the small caps but I've seen many a mobo that was completely dead totally due to bad 85°C 4 and 5 mm caps. Intel (brand) boards in sockets 370-423-478 had a lot of problems that way. (They were using quality Nichicon caps, but the VR series which is rated for 85°C.) Those are memorable to me because they had so freakin' many 4 & 5 mm caps needing replaced and they were a pita because they used extra tiny solder pads for those caps.
Anyway, 85°C caps + heat = dead mobo.
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