What does this capacitor symbol mean?


#1

This component smoked when I turned on a decades idle spectrum analyzer (Zonic+AND 3524 of 1990s vintage in like-new condition, visually) to see if I could use it for a field test. The company is no longer active and I have two giant user’s manuals but no maintenance info.

The component has a teardrop, rough-surface, dipped epoxy appearance with “10” and under that “35,” and “+” near one lead but no other I.D. It stands 3/8" above the board. The silk screen on the circuit board says, “C9,” but has an unusual (to me) symbol for a capacitor. The two parallel lines of the capacitor symbol have three diagonal cross-hatches between the lines, as shown in the photo.

I assume that this is a 10uF 35V tantalum cap and that the cross-hatches indicate some kind of transient voltage suppression in the device (the component goes from a trace to ground), but I can’t find the symbol on-line and am reluctant to simply substitute a common tantalum capacitor until I know what the symbol means. There are other identical components with the same symbol on the board and many capacitors with the ordinary capacitor symbol lacking the cross-hatching.

Any assistance appreciated.
Photos:


#2

@awright, I do not think there is anything special about this tantalum capacitor. I have seen the same labeling before. The way this capacitor is labeled is likely just a variation of a simpler style where an L-shaped symbol brackets the component’s capacitance and voltage labeling. The long vertical part of the L bracket is in-line with the positive component lead, which is also the longer of the two leads.

The only time I’ve seen this is on caps that are labeled “upside-down”, but that doesn’t mean can’t occur on caps that are labeled “right-side-up”.

This is my first post here on the Digi-Key Tech Forum, so I don’t know if the Forum software will allow me to post links, but I’ll try… Here is a link to a page that shows a tantalum capacitor that’s labeled as I described above. See the photo of the second capacitor from the top of the page:

http://www.learningaboutelectronics.com/Articles/Tantalum-capacitor-polarity-markings

As for your spectrum-analyzer. You might want to consider going around with an in-circuit ESR meter and look for any caps that need replacing. Look for bulging electrolytic caps. I would re-cap the tantalum caps as well. To limit wide-ranging damage (if it isn’t too late), Isolate circuit stages from each other and power them up one-by-one as you go along replacing bad caps.

Good Luck, David


#3

Hello awright, this would be a Japanese schematic symbol for an electrolytic cap used on older schematics.
take a look at this forum post here that will help explain it better, or you can google “japanese capacitor schematic symbol”


Unfortunately there isnt any official documents for that as its more of industry standard type of question.


#4

WOW!!! I am impressed! Two great answers before I could go reheat my coffee. And just the info I needed. Also good advice about replacing capacitors. I was aware that aluminum electrolytics fail with age but not that tantalums did also. It may be too late for my analyzer because when I took off the covers and cautiously turned it on (with my finger remaining on the switch) to locate the problem - nada. Silence. Darkness. I had to use the smell test. Wish me luck.

But does this mean that I should toss all my (hundreds - thousands of) tantalum caps accumulated over many years? Or would testing them at rated voltage on a bench power supply for a few days before installation suffice? Do Tantalums need “reforming?”

Many thanks, guys.


#5

Following up on my last comment: I searched my pullout components boxes and found a bunch of 10uF 50V aluminum electrolytics and four tantalums and decided to apply 31.5V (max from my bench power supply) to test/reform them. 3 of the four tantalums were short upon application of power! All of the aluminums were good and are doing fine after several hours. (I realize that I should have brought them up to voltage gradually.)

I have no way of knowing the age or history of abuse of any of them. All the tantalums and all the aluminums were identical, implying that they came from the same board(s) at the same time.

Lesson learned. I will be much more careful using salvaged caps in the future and definitely test/reform them under controlled conditions.