Chuck
¡°You didn't listen to what I said about the electrolyte.¡±
On the contrary, I ¡°listened¡± and paid close attention. I even quoted each part of your message, and commented on it in detail.
In the West, I understand that the cultural term ¡°to listen to somebody¡± sometimes means to hear them, to pay attention, then to AGREE with them, and to DO as they say.
Here, culturally, ¡°to listen¡± means to pay attention only. There is NO obligation whatsoever to agree with the speaker, or to do as he says.
So I have definitely listened to you, paid attention to you, but I am under no obligation to agree with you, even if you put forward what on the face of it, is a convincing argument, but is lacking in substance, proof and facts.
¡°The corrosive, to copper, electrolyte in 105C capacitors makes a mess out of copper, but does nothing to aluminum and aluminum oxide. An electrolyte can be corrosive to one material, and totally benign to another.¡±
Chemistry 101. No argument at all.
Chemicon¡¯s problem was the electrolyte destroying the capacitors from within, causing widespread shorts. The copper traces of the PCB¡¯s were unaffected. That modern failure is highly relevant to our discussion. Furthermore, that shocked the EE community, because Chemicon is one of the most reliable manufacturer's out there, and was generally trusted to do their homework, so that crap like that shouldn't happen.
The 90¡¯s failure of counterfeit electrolyte (Chinese manufacturers) is well-known, and may or may not have caused shorts when venting ¨C however there is not sufficient absolutely empirical evidence backed up with any manufacturer's data, to make a general claim.
¡°When you operate a modern electrolytic capacitor on lower than its nominal voltage rating, it is not harmed, and it does not change in any way.¡±
That¡¯s appears to be a convincing claim, but unless you can support that with absolute proof across all manufacturers, I cannot accept that. Chemicon¡¯s case refutes your assumption in its entirety.
¡°Today's 25V capacitor is yesterdays 50V capacitor.¡±
Can you offer any proof for that claim?
¡°If the electrolyte was as corrosive as you imagine, my bags of NOS capacitors would have all eaten away their aluminum oxide dielectric and all be short circuit. They are not. They are as good as the day they were made. Electrolytic capacitors from 40-50 years ago would be long gone in similar circumstances.¡±
I do not accept your supposition. You have a fact on the ground, and you have chosen a very convenient reasoning to ¡°support¡± the fact, but you know as well as I, that there is no proven relationship between the apparently "good" condition of your capacitors and the propensity of a given electrolyte to corrode under a working voltage load. Have you checked Dissipation, tangent and impedance of each capacitor against the manufacturer's data? Have you run the capacitor at the extreme temperature limits specified, and then rechecked the performance? Until you have that substantial empirical data, your claim is unsubstantiated.
¡°You are limiting your choices based on imagined problems.¡±
That¡¯s your conclusion, not mine. I have spent many years in a sensitive manufacturing environment under tight tolerances, and engineers were "encouraged" to research their proposals to be watertight if they wanted them to be considered for inclusion in production. Instead of hampering and discouraging suggestions, that policy caused excellence in the extreme.
-Chuck Harris
¡°OBTW, Nichicon of 1975 is a far different company from Nichicon of 2018. Dare we compare Tektronix of 1965 to the Tektronix of today? Neither company has any of the original founders, nor their instincts for quality, involved today.¡±
Would you like to stand up in court and defend that statement against Nichicon¡¯s lawyers? I doubt it. Tek, I¡¯ll agree with you. But using Tek's decline to stretch your reasoning to apply to Nichicon as well, is pushing your confidence into a very dangerous zone.
In short, you haven¡¯t provided me with any empirical statistically relevant proof that I should change my conservative habits.
I¡¯ll leave you with one thought. In light of your proposal to use massively overrated capacitors in all applications, then in these days of excessive cost-cutting and profiteering, one may propose to Nichicon¡¯s management: Produce only capacitors rated at 35V (smallest physical size 5mmx11mm), 63V (8mmx15mm) 100V (10mmx20mm). What a fantastic savings in production costs! Why have no capacitor manufacturers streamlined production like that? The profit potential must be enormous.
AND the BoM of appliance manufacturers would be vastly simplified. More profits.
No, I suggest to you that there are things that we don¡¯t always know about, in spite of your best intentions, and walking the tried and true path is the honest way to deliver best value to my customers.
There are reasons and considerations we don¡¯t even know about, and even if failures occur, nobody is going to admit responsibility.
This discussion has been stimulating, however, I remain unconvinced, and I will continue to use capacitors correctly matched to actual circuit voltage.
Any other users who choose to go overboard and install a 330uF 160V cap in a place where a 25V cap is required, is not only wasting his hard-earned money substantially, but may discover at some future point in time that the circuit becomes unstable. Or, he may not. I¡¯ll leave it up to users who choose those highly overrated caps, to post their experience in a few years. I¡¯m not holding my breath.
Menahem
