How can I find out if a cap is defective?

Ignacio49

New Member
Is there an easy way (easy for a newbie) to find out if a cap is defective/leaking without taking the cap out of the circuit?

I have a simple/non expensive portable digital L/C meter. Can I use it for that purpose?
 
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Thanks DeafbyKhorns - Your answer made me realize that my question was not exactly what I wanted to ask. I therefore changed it.
 
There is no way to test capacitors in circuit for functionality. Your LC meter will only measure the capacitance, and won't be able to test for shorts or leakage.

An ESR meter is the best available solution, and even it only provides a basic "go/no-go" test for electrolytic capacitors larger than 1 uF. It will not reliably test any electrolytics much smaller than that, and it's not useful for film caps, so it's not capable of testing coupling capacitors, for example.

The only really reliable test is to take the cap out of the circuit and test it using a dedicated capacitor tester, which will apply the full working DC voltage and measure any current leakage.
 
I have access to a Chroma 11200 Capacitor Tester but I’m not sure on all the proper settings for it. Voltage is easy, I’ll set it to the rated voltage of the Cap. The other settings are 1. Charge Current Limit (0.5mA-500mA), 2. Leakage Current Measurement Range (2uA, 20uA, 200uA, 2mA, 20mA), 3. Charge Time (0-999 S), 4. Dwell Time (0.2-999 S), 5. Measurement Speed (Fast, Medium, Slow). I will be using it to test my various Caps in my MC240. What Leakage value(s) are acceptable? Thanks for the guidance in advance!
 
even with meters/instruments that test "current" indicators of good health (esr, capacitance, working
voltage, ripple current) you can have caps that are defective in the audio chain - random noise,
hiss, and static. my dh101 had several such caps that measured perfectly but once replaced,
the noise(s) disappeared. my second recap in 40 years.

I would replace all electrolytic caps if they are 15+ YO, sooner if the brands are less than
top shelf (British term).
 
even with meters/instruments that test "current" indicators of good health (esr, capacitance, working
voltage, ripple current) you can have caps that are defective in the audio chain - random noise,
hiss, and static. my dh101 had several such caps that measured perfectly but once replaced,
the noise(s) disappeared. my second recap in 40 years.

I would replace all electrolytic caps if they are 15+ YO, sooner if the brands are less than
top shelf (British term).
Agreed! I wanted to test the caps I’m pulling out just to see their condition. So far the Black Beauties are coming back with around 1uA of leakage @ 600V. What value is considered not accaptable?
 
leakage is only one attribute, high or low depends on what folks have to say about
this particular item - IOW the manufacturer, years ago, may or may not have
specified what is good/bad/OK/in-range/sufficient/etc. today vendors may specify
a range for this and any differences inside/outside this range may not render the
cap unusable.

and there's the possibility that leakage is good, and something is not. again, if they're
electrolytics then they need replacing.

you can work out the voltage drop and depending on the circuit position, whether it
affects the sound or not.

do note that many gear/guitar heads swear by brands like tropical fish, bumble bees
so replacing them whether they are good/bad/indifferent may change the sound.
 
How much does the cap cost? If it's a small electrolytic, replace it with a decent Nichicon Muse or Fine Gold and be done with it. Depending on size, they range from about seventy-five cents to two dollars. You would have to remove it from the circuit board to test it anyway. Depending on age, would you want to put it back even if it measured good?
 
agree with @jlovda!

replace all the electrolytic caps, with newer ones. Black beauties and even Black gates
(anything "black" - green Nichicon Muse ESs are the new black - for spooky "black" backgrounds)
have been out of production for a while and will soon enter replacement phases due to age
(like knee, hip replacements, etc)

short list of abbreviated comments/notes
1. replace <4uf ecaps with (stacked) films of any material (esp tantalums)
2. use non-polars for signal-path decoupling (better sound AND prevents explosions)
3. use brand name ecaps for PS and add bypasses @1/10 or 1/100 values
4. do one-at-a-time (pull, measure old, get new, measure new, solder new in, test)
5. do not correct anything you think is a mistake (PCB stencil markings, schematic, parts list)
replace exactly as it was in the working unit. re-engineer if you are talented, knowledgeable,
experienced, etc
6 do not change values when replacing unless you document why.
7. resistors: replace with like kind (CC, CF, MF, etc) unless you want different house sound

there are hundreds of threads here on AK for all the above. reading a few will allow the
lightbulb to go on and light your future. return the favor to AK by documenting your journey
and especially if you get help from AKers.
 
agree with @jlovda!

replace all the electrolytic caps, with newer ones. Black beauties and even Black gates
(anything "black" - green Nichicon Muse ESs are the new black - for spooky "black" backgrounds)
have been out of production for a while and will soon enter replacement phases due to age
(like knee, hip replacements, etc)

short list of abbreviated comments/notes
1. replace <4uf ecaps with (stacked) films of any material (esp tantalums)
2. use non-polars for signal-path decoupling (better sound AND prevents explosions)
3. use brand name ecaps for PS and add bypasses @1/10 or 1/100 values
4. do one-at-a-time (pull, measure old, get new, measure new, solder new in, test)
5. do not correct anything you think is a mistake (PCB stencil markings, schematic, parts list)
replace exactly as it was in the working unit. re-engineer if you are talented, knowledgeable,
experienced, etc
6 do not change values when replacing unless you document why.
7. resistors: replace with like kind (CC, CF, MF, etc) unless you want different house sound

there are hundreds of threads here on AK for all the above. reading a few will allow the
lightbulb to go on and light your future. return the favor to AK by documenting your journey
and especially if you get help from AKers.
Thanks for the Tips! I have ordered most of these parts from Jim McShane, who seems to be a wealth of knowledge on these. I have reviewed multiple threads and have to say this is a great place with wonderful members! It's pretty exciting going through Historical Audio Equipment.
 
Someone on this forum had a very good test for old electrolytic caps. Remove from equipment and toss into nearest trash can, if it makes a noise when it hits the bottom of the can, it's bad.
I kinda like that test.........

BillWojo
 
@BillWojo - great idea!

mine is to save them all, id them and wait for the cap/burn-in deniers and have them
test any/all I have found defective (music not measurement) and start a billion dollar
company that IPOs in a week.

no takers.
 
Someone on this forum had a very good test for old electrolytic caps. Remove from equipment and toss into nearest trash can, if it makes a noise when it hits the bottom of the can, it's bad.
I kinda like that test.........

BillWojo
LMAO!!! OK, that's one way to do it :)
 
@BillWojo - great idea!

mine is to save them all, id them and wait for the cap/burn-in deniers and have them
test any/all I have found defective (music not measurement) and start a billion dollar
company that IPOs in a week.

no takers.
Ohh I will at least save mine just to have the original parts with the Amp. Not that I plan on ever selling it, but there's something about having the originally installed parts with the vintage gear. Better than Land Fill!
 
There is no way to test capacitors in circuit for functionality. Your LC meter will only measure the capacitance, and won't be able to test for shorts or leakage.

An ESR meter is the best available solution, and even it only provides a basic "go/no-go" test for electrolytic capacitors larger than 1 uF. It will not reliably test any electrolytics much smaller than that, and it's not useful for film caps, so it's not capable of testing coupling capacitors, for example.

The only really reliable test is to take the cap out of the circuit and test it using a dedicated capacitor tester, which will apply the full working DC voltage and measure any current leakage.
The Chroma 11200 Tester is able to reliably test for leakage. Even the small .02uF caps. Not in CIrcuit mind you. http://www.chromausa.com/pdf/Br-11200-Leakage Current_IR Meter-032007.pdf
 
I replace the lot, sometimes I test them just out of curiosity, but they are all headed for the "round filing cabinet"....
I have never had an instant where the amp/tuner whatever sounded worse with new caps, always an improvement in my experience...
 
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