Need help finding replacement SMD part.  - Page 1
Forum section: electronics / projects

author: electronics-whiz
author_rank: Regular Contributor
timestamp: March 01, 2016, 01:57:17 am
content: I have a couple of older 3com 3C995-SX network cards, one of them seems to be missing an AMD capacitor, I did find an SMD ceramic cap and small inductor missing too, but they were in the box with the card, not sure where this larger part went though. Hoping to maybe see if I can fix it.I was able to take the other card and find what parts go where and value of the missing capacitor.The part I'm missing has 3 lines on it that look like this:15516k228I did a google search to try and find a legend to these codes and it seems that this cap is 155PF, 16 Volt, Kemit code is K, date=228The PCB says it's a capacitor, has polarity marking and a + on the PCB by the band on the cap. Looking at pics parts that match this and are yellow are tantalum capacitors, but I'm not totally sure on that just going off picture.I was also haveing hard time finding a part the same size. Measuring it I get 2milimeter wide, 3 millimeter long (lead end to lead end).I looked on Mouser all they had was ceramic caps, I don't have this in my collection of parts. (I'm in the USA if it helps.) Wondering where I could find this part, and could order a couple of the them or maybe a dozen if I had to. If I have something wrong in my info feel free to correct me so I don't order the wrong part. Or would I be better off trying to get a through-hole style part like this and using that instead and maybe just glueing it down?Thanks

author: exmadscientist
author_rank: Frequent Contributor
timestamp: March 01, 2016, 04:49:54 am
content: I think you'll have better luck if you can post a picture rather than just trying to describe the thing.It sounds like a fairly standard tantalum capacitor, but tantalums are not made as small as 155pF. Interpreting "155" with the usual scheme for capacitors, as "15×105pF" gives 1.5uF, which is plausible but on the small side. "228" likewise would be 2200 uF, which is far too large for a part of that size. (Is there any way it could read "226"? That's 22uF, a rather common size.) "3 millimeter long" by "2 milimeter wide" sounds like a 1206/M3216 (3.2mm × 1.6mm) part, again very common. But the size is not so important as long as you can physically get the replacement mounted.

author: electronics-whiz
author_rank: Regular Contributor
timestamp: March 13, 2016, 07:35:45 pm
content: I was just doing some more looking into and I foud the code thing said 1.5 UF. A couple friends into electronics told me I would probably be able to just throw a through hole electrolytic or tantalum on solder leads down and then glue it down.1.5 UF is quite small for electrolytic though and the tantalums I have I think are too small, but may be able to combine them.I have one good cap on a matching board I'll try and measure it and get a pic and post.

author: electronics-whiz
author_rank: Regular Contributor
timestamp: March 13, 2016, 08:00:51 pm
content: Image with pencil tip for scale. couldn't find a way to capture the writing on it, but did double check the values from my first post match.

author: Whales
author_rank: Super Contributor
timestamp: March 13, 2016, 10:42:44 pm
content: Hold your camera further away from the board to fix the focus. Crop the resulting image to zoom it in. You'll get a much clearer shot.

author: electronics-whiz
author_rank: Regular Contributor
timestamp: March 13, 2016, 11:46:49 pm
content: I was able to get it working with some modification. Found I had gobs of 1UF electrolytics, found a few .47UF sired together in parallel ran a few inches of wire to the original solder pads, hot glued the soldiers, wires, caps down seems it works again.