How to chek other than Electrolytic Capacitors ?

aljamri · Jan 5, 2008

Hi everybody,
As a maintenance guy, I get many discarded boards from faulty equipment. I spend sometime on removing their components, check them and sort them for future needs. Resistors, diodes, transistors, LEDs, and Electrolytic Capacitors are easy to test, but the other than Electrolytic Capacitors such as ceramic and tantalum can not be checked. Is there any way to check them?

Thanks

Hero999 · Jan 5, 2008

Ceramics don't normally go bad but if they do I assume they go short circuit as the dielectric has been damaged. I suppose it's possible for them to go open circuit but the only way I can see it happening is if it's been mechanically damaged, i.e. the ceramic is chipped and the wires are starting to come loose.

Nigel would disagree but I've never seen any tantalums go bad but according to him they fail short circuit which makes things easy.

I would check both ceramics and tants on a multimeter with the resistance setting, they should read open circuit, then with the capcitance setting, they should be within their rated value by about 20%.

If your meter doesn't have a capacitance setting then you can make your own very basic capcitance meter with an astable multivibrator like the 555 timer.

ericgibbs · Jan 5, 2008

You could build this tester:

http://members.shaw.ca/swstuff/esrmeter.html

audioguru · Jan 5, 2008

I have had many tantalum capacitors "disappear". All that was remaining was their two short wires. They were 25V and 35V ones operating at regulated 15V and they blew up.
I have never had an electrolytic capacitor fail on any of my projects.

I have also never had a diode, transistor or IC fail on any of my projects for 48 years.

Nigel Goodwin · Jan 5, 2008

Hero999 said:
Nigel would disagree but I've never seen any tantalums go bad but according to him they fail short circuit which makes things easy.

No - not easy! - imagine a board about the size of an A4 sheet of paper, covered with components, with tantalum capacitors all over, many on the same HT rails. You know it's got a S/C tanalum on a specific rail, but there are LOT'S of them all over the board on that rail!.

But for checking them after removing them, obviously easy! - if they aren't short, they are almost certainly OK.

felis · Jan 5, 2008

Hero999 said:
I suppose it's possible for them to go open circuit but the only way I can see it happening is if it's been mechanically damaged, i.e. the ceramic is chipped and the wires are starting to come loose.

This kind of fault happens quite frequently. Many modern (20 years or younger) ceramic leaded capacitors are simply 1206 SMT parts with leads soldered to it. The whole thing then gets covered with epoxy. When one tries to extract it, solder joint inside the cap fails from mechanical stress/overheating.

Speakerguy · Jan 5, 2008

My Fluke 177 seems very accurate at measuring capacitance. It has a range of 1nF up to a 10,000uF. It seems very accurate even at the very low end of its range. It is an expensive meter but if you do a lot of work it may be worth the expense.

audioguru · Jan 5, 2008

felis said:
This kind of fault happens quite frequently. Many modern (20 years or younger) ceramic leaded capacitors are simply 1206 SMT parts with leads soldered to it. The whole thing then gets covered with epoxy. When one tries to extract it, solder joint inside the cap fails from mechanical stress/overheating.

Some guys use a blow torch to desolder parts.
Other guys us a soldering iron without temperature control to desolder parts.
Same thing.

My temperature controlled Weller soldering iron never overheats anything.

Hero999 · Jan 5, 2008

I've used a non-temperature controlled heat gun to desolder electrolytic capacitors before and watched them all pop like caps in a toy gun.

aljamri · Jan 6, 2008

speakerguy79 said:
My Fluke 177 seems very accurate at measuring capacitance. It has a range of 1nF up to a 10,000uF. It seems very accurate even at the very low end of its range. It is an expensive meter but if you do a lot of work it may be worth the expense.

My Fluke 179 gives me "DISC" indication for non-polirized capacitor, or there is another setting i mesed?

aljamri · Jan 6, 2008

audioguru said:
My temperature controlled Weller soldering iron never overheats anything.

What is the best degree, for me below 300 C seems not hot enough, so that is my normal working Temp. but sometimes i increase it upto 400 espicaly for removing old components.

aljamri · Jan 6, 2008

ericgibbs said:
You could build this tester:

http://members.shaw.ca/swstuff/esrmeter.html

Thanks for the link, during googling for the matter i came across ESR tester, so i was welling to know about it. I'll read and try to do it.

Thanks again

audioguru · Jan 6, 2008

I use a Weller tip that is a 1/16th inch "oval shape" and is rated at 700 degrees F. Each solder joint takes 1 second. Desoldering also takes takes 1 second (slurp!).

felis · Jan 6, 2008

aljamri said:
What is the best degree, for me below 300 C seems not hot enough, so that is my normal working Temp. but sometimes i increase it upto 400 espicaly for removing old components.

Make sure the tip of the iron is clean and tinned - good thermal contact is essential. I use 550 degrees F which is 287degC. Sometimes when I need to solder something big (like TO-220 tab) I bump it to 650F (343C). 400 seems a little bit excessive - not only will will you increase the chances of damaging the part, but the tip of the iron will be burned off quicker.

Nigel Goodwin · Jan 6, 2008

If it's any help, I leave mine set at 300C - seems fine for both leaded and unleaded.

Krumlink · Jan 6, 2008

audioguru said:
I have had many tantalum capacitors "disappear". All that was remaining was their two short wires. They were 25V and 35V ones operating at regulated 15V and they blew up.
I have never had an electrolytic capacitor fail on any of my projects.

I have also never had a diode, transistor or IC fail on any of my projects for 48 years.

Tants are VERY sensitive to voltage spikes, so they usually use a value x3 of the maximum Voltage, aka you would have wanted to use 50V Tantys.

kchriste · Jan 6, 2008

audioguru said:
I have had many tantalum capacitors "disappear". All that was remaining was their two short wires.

Where I used to work, they had a 35ft ceiling in the manufacturing dept. Several people had tantalum caps hit the ceiling upon powering up a board for testing. It certainly encouraged the use of safety glasses.

felis said:
Many modern (20 years or younger) ceramic leaded capacitors are simply 1206 SMT parts with leads soldered to it.

It's funny how the laws of supply and demand cause such a strange way of making something. Here a pic of a glass encapsulated SMT capacitor with axial leads from my junk bin:

crusty · Jan 6, 2008

quickest way i know to check them without a meter is grab one around the same farads, hold it with something other than your hands, and connect it to the solder points on the other side of the board while it's on, if it gets rid of your problem, replace it!

kchriste · Jan 6, 2008

Crusty,
That'll only work if the capacitor is open. If it is shorted, you'll see no change.
Also, you must be careful when doing this, especially with larger caps at higher voltages, because the surge current can damage other components.

crusty · Jan 6, 2008

kchriste said:
Crusty,
That'll only work if the capacitor is open. If it is shorted, you'll see no change.
Also, you must be careful when doing this, especially with larger caps at higher voltages, because the surge current can damage other components.

sometimes if you don't have the right tools or money, you have to improvise.

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How to chek other than Electrolytic Capacitors ?

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