Is it Tantalum? - Page 1
Forum section: electronics / repair

author: TheEnd
author_rank: Contributor
timestamp: October 03, 2020, 08:11:47 pm
content: So I'm taking a look at an engine ECU that's had 24v into it.Three of these capacitors were showing as shorted, and once removed and checked out of circuit, it was confirmed.My first thoughts were just to get another three of these capacitors, solder them back and see if things improve.I've got a yellow square with 333K on it, and to me, that means 33nF, 10% Tolerance, tantalum.Looking around, I can't seem to find SMD tants in 33nF, and also there's no polarity marking on them either, so I'm starting to question what these actually are.This was out of engine electronics from the late 90s, and I've since spotted another "333K" marked yellow square in a more modern 2010 engine ECU, also with no polarity marking.Mouser, RS, Farnell, Digikey etc only have 33nF Tantalums as axial, so have I just assumed its gender because it's yellow?!?

author: TimFox
author_rank: Super Contributor
timestamp: October 03, 2020, 08:57:54 pm
content: They look too large to be a MLCC ceramic--I suspect that they are film capacitors.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 04, 2020, 12:19:18 am
content: I'd say tantalum for second picture, inductor for third.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2020, 12:47:45 am
content: The last one is the "more modern" one? The logo looks to be EPCOS, admittedly a bit hard to tell with the bloppy inkjet printing.Is a bit suspicious that the markings are so similar. I don't recognize S+M, maybe you can find who they were, or who acquired them since? Agree, it's likely tantalum in the first one (335 = 3.3uF) and the smaller one inductor (333 = 33uH most likely).Don't think I've seen encapsulated SMT films before; they're always the open stacked type?Tim

author: Psi
author_rank: Super Contributor
timestamp: October 04, 2020, 02:53:06 am
content: If you can measure the voltage across it while running you can tell if it's a tantalum.With tantalums the white line on top is positive, while other caps are line negative.

author: cgz2001
author_rank: Contributor
timestamp: October 04, 2020, 04:06:56 am
content: The “A” insignia at the top is avx. These are chip inductors. I had the same question lately when I saw them in one of my projects a couple months ago. Measure the inductance and you’ll find it’s something like 333nH for 333k, if I recall correctly.

author: srb1954
author_rank: Super Contributor
timestamp: October 04, 2020, 11:40:54 am
content: Quote from: T3sl4co1l on October 04, 2020, 12:47:45 amS + M might stand for Siemens & Matsushita which later became EPCOS.

author: Kjelt
author_rank: Super Contributor
timestamp: October 04, 2020, 11:47:04 am
content: AFAIK a tantalum cap besides its capacity always has a polarity indicator (brown line in the above picture) and a max operating Voltage (which you have to dereference with at least 20-40% in practice), 25V in the above picture, on its package.So I would say only the first picture is a tantalum cap, the rest non polarity passive component could be a cap or inductor.

author: TheEnd
author_rank: Contributor
timestamp: October 04, 2020, 04:08:08 pm
content: Thanks guys, so a little bit of clarification, the tantalum in the first pic, upper left, isn't an issue, it was the smaller 333K component which was a mystery.An inductor could be right, maybe they weren't damaged at all!There were soldering marks around them, a burnt tantalum on the opposite side, and a shattered ceramic and resistor.I'm guessing my learning for today is "all that is yellow is not tantalum"That's assumptions for you, they were showing shorted/low resistance. My first thought with all three showing similar was another shorted component on a rail somewhere, but I decided to take them off and check.No polarity, voltage rating, and the fact that tantalums don't seem to be available in 33nF started to ring some bells.I'll check the other 333K component from a newer ECU which should be OK and see what it measures as.That could give a better clue

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 04, 2020, 04:28:27 pm
content: I have similar parts in my saved parts stash (IIRC some are marked S+M), they're all closer to shorts than capacitors and if I try to fuse the short out they don't give that nice Tantalum whiff.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2020, 04:52:14 pm
content: Quote from: srb1954 on October 04, 2020, 11:40:54 amAhh, that explains why I don't see many Panasonic (Matsushita) tantalums. Which, hmm, let me see; Digikey shows a few Panasonic parts, all "obsolete". Makes sense.Know I've seen Siemens with the "SH" logo before, which became EPCOS. Which, apparently that particular logo was discontinued in 1973? Those components aren'tthatold are they?..Tim

author: Bud
author_rank: Super Contributor
timestamp: October 04, 2020, 05:30:17 pm
content: Look at the connections of the part in question in the second photo. The bottom pad comes from some circuit , the top pad is a star connection to what appear to be DC bypass ceramic capacitors. It makes sense if the part is an inductor, through which the VCC or bias voltage is supplied. It would make no sense to have a tantalum connected to a star point bypassed by a bunch of ceramics.Since the markins on the part in the third picture is similar to that of in the second one, the third part is also an inductor.

author: james_s
author_rank: Super Contributor
timestamp: October 04, 2020, 05:42:36 pm
content: They are inductors for sure, I have used some very similar looking parts in the past. I have some of the same style that are black too.