Help me identify this diode/cap - Page 1
Forum section: electronics / repair

author: ESXi
author_rank: Regular Contributor
timestamp: October 17, 2019, 11:46:51 am
content: Yo,Got a controller board from a IR cam. Cam hadliquid & fire damagealso the digital video out female connector was roasted so internallydisconnected the ribbon flex cable but inside it was looking all fine and board had conformal coating all over the parts.So I tried to inject power with my bench power supply here at work (Yes I tried the correct voltage according to the datasheet). Turn out this bench power supply is crooked as f*ck .. garbage...Idk what happend but I set the current limit and voltage, nothing happend, so turned it up a little more and suddenly I hear some relay clicking and poof magic smoke released..My guess is that it is a cap (47 mike, 20 volt), on the input regulation board, hopefully the board still works or I'll be kinda mad at myselfBecause just before the dang thing blew up I saw some RS232 output in my terminal, so the brainbox was working ! (Made in Germany)What ya guys think it is? I might be lucky or not.

author: PKTKS
author_rank: Super Contributor
timestamp: October 17, 2019, 12:12:26 pm
content: from here looks like tantalum (even elco) CAP47 per 20 w/marked polaritymy SMD readings are pretty much frustrating amusingwaste of my time... 50% are bad.. some few percents matchPaul

author: Psi
author_rank: Super Contributor
timestamp: October 17, 2019, 12:27:16 pm
content: Check if the line is on positive side. If it is then it's definitely a tantalum.They use a line to signify positive unlike normal caps.My guess would be 47uF 20V

author: ESXi
author_rank: Regular Contributor
timestamp: October 17, 2019, 12:31:10 pm
content: Quote from: PKTKS on October 17, 2019, 12:12:26 pmHi Paul,I think we're on the same track. I searched on google images and digikey a bit. Seems to be a293D Solid Tantalum Surface Mount Chip Capacitorshttps://www.vishay.com/docs/40002/293d.pdfThat might be the one I am looking for. Let's see what other members have to say, if they can also confirm it.

author: ESXi
author_rank: Regular Contributor
timestamp: October 18, 2019, 07:59:28 am
content: You won't believe this crazy sh*tWent to my local electronics shop in town after work purchased a fresh electrolytic capacitor. Dropped a 47μF 50volt jobby in it, the guy tried it for me on his power bench in the shop (before I replaced the cap). He told me the camera was dead as a brick. I still purchased the parts because I wanted to give itone more try.Made in Germany!At first the output on the TV was messed up but I had the coax connector wired up wrong (analogue video output CCIR), it was a 50/50 shot. So you can see in the picture below it powers on and self test (POST), wow!

author: John.S
author_rank: Contributor
timestamp: October 18, 2019, 08:14:38 am
content: Hi,Mayby I am wrong, but it seems to me you have the new cap the wrong way around.In the doc about the SMD cap the white band indicates the + side of the cap.The new axial cap has ( as far as I know) the white band on the - side.gr. John.

author: ESXi
author_rank: Regular Contributor
timestamp: October 18, 2019, 08:20:28 am
content: Quote from: John.S on October 18, 2019, 08:14:38 amWtf I see it in the datasheet, indeedIs this the case for all the SMD stuff? hmm Well, the cap didn't blew up. Let me try it the other way around when I get home.Strange, the white band is normally always the negative terminal (for non SM parts)?Edit: removed the short but added the cap the wrong way. I'll admit, I'm not a electronic engineer. Just a hobbyist a/k/a newb.

author: mariush
author_rank: Super Contributor
timestamp: October 18, 2019, 08:30:18 am
content: For electrolytic capacitors, yes, the convention is that the line is negative.For tantalum capacitors and some surface mount polymers, they indicate positive with the line or with a plus printed on the positive side.Also, to keep in mind for future, some manufacturers use the line on the silkscreen for positive.. Pegatron group (Asus, Asrock etc) is "famous" for this... see for example the images in this article :https://www.eteknix.com/asrock-e3v5-ws-intel-c232-motherboard-review/2/The electrolytic you used was probably damaged a bit but i guess should still be fine.

author: ESXi
author_rank: Regular Contributor
timestamp: October 18, 2019, 08:35:36 am
content: Quote from: mariush on October 18, 2019, 08:30:18 amYou're never too young to learn. So now I know, lol.Quote from: mariush on October 18, 2019, 08:30:18 amDid short tests of less than 1.5 minute also the cap was originally rated at 20 volts, I've used a 50 volts one. The shop had no 20 volts so.Might be just fine, let me try and see what happens when I get home

author: ESXi
author_rank: Regular Contributor
timestamp: October 21, 2019, 12:00:58 pm
content: That was really odd, I change the polarity of the capacitor, but it made no difference at all (camera did the exact same thing). Strange hmm.Ahh well.. It was fun playing with it