Caps: what is more important, ESR or age?

MajorHavoc

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If I have a 30 year old cap whose ESR is half of the one I just purchased, should I install the new one?
 

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I think the words "30 year old cap" answer your question.

Really? Even though the ESR is 2x better (and still in the good range) on the "30 year old cap"?

I got a cap kit with 7 caps in it. One new cap was bad and 3 new caps had worse ESR ratings than the ones on the board. If I just installed the kit blindly, I could be worse off than I am now!

I am just trying to understand when to follow the ESR meter and when to follow other factors.

Thanks!
 
Really? Even though the ESR is 2x better (and still in the good range) on the "30 year old cap"?

I got a cap kit with 7 caps in it. One new cap was bad and 3 new caps had worse ESR ratings than the ones on the board. If I just installed the kit blindly, I could be worse off than I am now!

I am just trying to understand when to follow the ESR meter and when to follow other factors.

Thanks!

:D

what is this for? where did you get your caps from? I think Nichicon and like one other brand are the preferred kind by people on here.
 
If it's capacitance is still what it should be then there's absolutely no point replacing it as far as I'm concerned.
That is not really true. Capacitance is a measure of total charge that a capacitor will hold. ESR is a model of how the part can deliver current. It's not a perfect analogy, but think of one like the size of a gas-tank and the other like the delivery hose. They're different measures and one can look fine while the other is inadequate.

If I have a 30 year old cap whose ESR is half of the one I just purchased, should I install the new one?
Install the new one it if the capacitor is causing a failure on your circuit board. Otherwise don't obsess about it. Yes ESR is a good indication of the health of the capacitor but:

- Check the entire part-number of both capacitors. Maybe you're comparing some high-quality audio grade capacitor to a cheap general purpose capacitor? Or different temperature grades? You only said "half the old one". Maybe you're comparing awesome to average?

- Consider the purpose of this capacitor in-circuit. Are you fixing a switching power supply with high frequency AC signals where ESR matter? Or are you just worried because you own the tool and saw a big number? There are lots of applications this hobby where it's just not very critical.

It's easy to get led on a wild goose chase... the question shouldn't be if the component is perfect, it should be if the component causes a failure. Another analogy, sometimes you need regular octane gas and sometimes you need premium.
 
If the new cap specs out properly, I wouldn't worry about the ESR rating on it. Different caps from different manufacturers and runs have different ESR ratings anyway.

I only use my ESR meter to find obvious fault with caps in circuit. It's not my end-all be-all tool as far as capacitors go.

AFAIK, the only way to effectively use an ESR meter to check caps is to compare several caps that are exactly the same in every way to the suspect cap. If the suspect cap stands out clearly from the rest (usually close to ten times the ESR) then it's floated and bad.

Your new caps are probably fine. As long as their ESR falls within an acceptable range, I wouldn't worry about them.

Here's a nice little ASCII chart I found in the Blue ESR meter manual - it gives the 'max value' for each of several common capacitor types. Again, this is not GOSPEL - use it merely as a guide to find caps that 'stand out from the crowd' so to speak.

http://members.ozemail.com.au/~bobpar/2003esrchart.txt
 
Really? Even though the ESR is 2x better (and still in the good range) on the "30 year old cap"?

I got a cap kit with 7 caps in it. One new cap was bad and 3 new caps had worse ESR ratings than the ones on the board. If I just installed the kit blindly, I could be worse off than I am now!

I am just trying to understand when to follow the ESR meter and when to follow other factors.

Thanks!

Out of curiosity, what brand are the new caps with the higher ESR?

Ed
 
That is not really true. Capacitance is a measure of total charge that a capacitor will hold. ESR is a model of how the part can deliver current. It's not a perfect analogy, but think of one like the size of a gas-tank and the other like the delivery hose. They're different measures and one can look fine while the other is inadequate.
I'm perfectly aware of that..
 
The age of the caps is pretty irrelevant, whether they are good or bad is all you really need to know, and the ESR is the primary indicator of whether it has dried out or not. The capacitance may not actually change. Often you find only one specific type of cap is bad on any given board, eg all the 1uF may have high ESR, whereas all the 10uF are fine, even if they are the same make.
 
I finally installed the cap kit on my Galaga boardset last night, minus the bad cap, and it solved my problem. The problem was a HUGE current draw on the +12V at start up and then occasional current kicks that would result in a thump on the audio.

The bad new cap was a Sprague, I think.

Code:
Location  Value   ESR      New ESR
========  ====    ===      =======
C1 (Vid)  470/16  0.17     0.21
C25       10/16   6.0      1.0 (10/63)
C1        470/16  0.19     (BAD)
C20       22/35   5.8      1.0
C21       220/25  87       0.25
C22       100/16  0.78     0.56 (100/25)
C44       10/16   5.3      1.0 (10/63)
 
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Nice. I just got a blue ESR meter kit for christmas. I haven't used it yet, but am hoping it will be a great tool in my kit.

So do you guys with ESR and cap meters just check the common caps now and only replace what's bad instead of a full shotgun capkit? Any recommendations for a hobbyist capacitance meter that is in the range of the caps we typically deal with?
 
I, too, just got the Blue ESR meter for Christmas, and I've been using it all over the place - found some bad caps in a few dead LCD monitors I had, fixed them right up.

About arcade monitor chassis.....I'm inclined to change out ALL the caps when I have the kit, only because I really don't want to leave anything in there that's marginal. Plus, for RESALE value, it means more to other people to hear that the whole thing has been recapped, even though I know that just changing out the problem caps ONLY would probably have given the same result.

Plus, it's only like $10 for a cap kit. On a game (and hobby) that I spend lots more than that on. Saving $5 on half a kit that I don't change is not really worth if if I need to crack the game open again in a few months because more caps have failed again.
 
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