Cornell Dubilier - WBR capacitors why so expensive

[Jester]

I'm replacing most of the old electrolytic caps in an old piece of test gear and they have used a few 100uF, 50V  that are quite large (1.5" x 0.5") for their value and quite expensive. BOM calls for BR100-50, the actual cap installed is a WBR100-50. This is an 85 deg C cap, 2000hr, ESR3.9  , the tolerance is -10 to +150%, but  nothing exotic except the price $10.

In comparison Nichicon TVX1H101MAD are <$2, 1/4 of the size, similar specifications except+/-20%

Or if the +150% is important an Illinois Capacitor 157TTA050M (150uF) $1.46

Why are these so physically large and expensive?

[xani]

Quite plainly tech got better. Just make sure ESR difference doesn't matter for the place they were used and you should be golden

[james_s]

Do check the ripple current rating as well. A physically large capacitor will often have a higher ripple current rating, it has more mass and surface area to dissipate the power.

[Jester]

Re ripple current, I can't find the original data sheet, however the WBR 100-50 , shows 140mA@120Hz and the newer capacitors specify 220mA and 285mA, so I don't see ripple current as an issue.

I have attached the schematic of the circuit,  see C32, with the 3k resistors connected the ESR seems irrelevant. The other two are just bulk capacitance at input of voltage regulators.

JD, good eye I should have noticed, I corrected the schematic

[Jay_Diddy_B]

Hi Jester,
the polarity of the capacitor C32 is shown incorrectly. It should be negative end to the junction of R99 and R100.

It is a bootstrap circuit that increase the current in R99 when the output swings towards the negative rail.

Jay_Diddy_B

[Jester]

Hi Jester,
the polarity of the capacitor C32 is shown incorrectly. It should be negative end to the junction of R99 and R100.

It is a bootstrap circuit that increase the current in R99 when the output swings towards the negative rail.

Jay_Diddy_B

Good eye, I corrected the schematic. Thanks.

I'm going to go with the $1.50 capacitor, makes me wonder why anyone would spend $10 on a capacitor with inferior specifications when a Nichicon or IC is a fraction of the price?

[james_s]

Repairing existing equipment? Because they like the brand name? Some other characteristic? It's entirely possible that the original engineer selected a part that was not the most economical available. Cornell Dubilier is a typically expensive brand that has made a lot of high end high quality parts. Whether the cost is justified depends, it's possible that they were excellent parts when designed and now getting a bit old. It's also possible that they were not always so much more expensive, it's common when a manufacture plans to discontinue something to first increase the price to discourage its use.

[Jester]

Repairing existing equipment? Because they like the brand name? Some other characteristic? It's entirely possible that the original engineer selected a part that was not the most economical available. Cornell Dubilier is a typically expensive brand that has made a lot of high end high quality parts. Whether the cost is justified depends, it's possible that they were excellent parts when designed and now getting a bit old. It's also possible that they were not always so much more expensive, it's common when a manufacture plans to discontinue something to first increase the price to discourage its use.

Yes, a Clarke-Hess calibrator.

That makes sense, the components are all high quality and they used quite a few CDE caps.