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 The company is no longer active and I have two giant user’s manuals but no maintenance info.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.


#6

The symbol denotes an electrolytic, tantalum, etc capacitor that is a “chemical-layered” unit. ( you wont find that in text books, its a description of composition). There was a company called “Chemi Con” that made early electroltyics and the description sort of examples their company name.

In early days of radio and electronics, all they had were air variable, ceramic, mica, treated paper and other solid dielectric capacitors with a “homogeneous” dielectric (the entire dielectric was basically the same material.

The symbols were parallel plates with nothing in between. Some had one curved plate instead of flat, and some had arrows to denote adjustability.

With the advent of “chemical capacitors” such as electrolytics, the shaded dielectric symbol came into use. It is universal, not just Japanese.

As to reforming capacitors, DO NOT UNDER ANY CIRCUMSTANCE try to reform, use or reuse OLD TANTALUMS. They tend to leak badly and EXPLODE. Old electrolytics without safety vents, and tantalums that are epoxy dipped (including SMT) will explode violently under certain “thermal runaway” situations such as high internal leakage. The epoxy dipped tantalums are sealed inside a hard, epoxy shell that can go off like a firecracker and throw pieces. They have no pressure vent. They were used for a high product-C-V back in the day when electrolytics werent much to write home about, but with advancements in capacitor technology, they are more or less a thing of the past.

As to installation of the tantalum unit in the photo, its installed with spacer collars (probably for wave soldering), but this may cause excessive stress on the lead entry to the capacitor- the spacer can cause a sharp bend at the body- avoid that.


#7

I don’t think there is anything uncommon about this tantalum capacitor. I have seen the equivalent naming previously. The manner in which this capacitor is marked is likely only a variety of an easier style where a L-molded image sections the part’s capacitance and voltage naming. The long vertical piece of the L section is in-accordance with the positive segment lead, which is additionally the more drawn out of the two leads.

The main time I’ve seen this is on tops that are named “topsy turvy”, however that doesn’t mean can’t happen on tops that are marked “right-side-up”.

This is my first post here on the Digi-Key Tech Discussion, so I don’t know whether the Gathering programming will enable me to post joins, however I’ll attempt… Here is a connection to a page that demonstrates a tantalum capacitor that is named as I depicted previously. See the photograph of the second capacitor from the highest point of the page:

Concerning your range analyzer. You should need to consider running around with an in-circuit ESR meter and search for any tops that require supplanting. Search for swelling electrolytic tops. I would re-top the tantalum tops too. To restrict far reaching harm (on the off chance that it isn’t past the point of no return), Disengage circuit stages from one another and control them up one-by-one as you come supplanting terrible tops.


#8

As mentioned… its a Japanese notation of a standard electrolytic capacitor. The Schematic symbol used on the board does not denote a special kind of capacitor. While not used as much today, it is very prevalent in older schematic diagrams that were designed by Japanese engineers… it does NOT mean you need to use a special Japanese manufactured capacitor. Its just the Symbol that they used for polarised electrolytic capacitors.