SMD Component Identification Assistance - Page 1
Forum section: electronics / repair

author: Garywoo
author_rank: Contributor
timestamp: August 23, 2018, 01:49:17 am
content: Hi everyone,I've never had to decipher an SMD code before, so I thought I'd run my thoughts past you bunch of helpful folks to make sure I'm on the right track.I've identified a failed SMD transistor (shorted) on an LED light strip controller PCB. The transistor outputs directly to the LED strip. There are 5 on the board, one for each colour channel (one removed in photo for testing).The board runs on 24v from a CV 0.83A 20W power supply.I'm pretty sure the component is a SOT-23 package. Length and width seem about right.The markings on the component are WKC 72. I'm not quite sure which part of the marking is significant. I usedthis codebookas a reference. Initially I thought theWKCwas the important part. This lead me toBCR119However I'm not sure if this is right. If the72is the important part, then it could be2N7002The silkscreen designates the component with an M. MOSFET? I'm thinking the 2N7002 is most likely correct. Am I correct in my assumption?Looking atoctopart, they come in a variety of continuous drain currents. What would be a safe choice for my application?Thanks for any help or advice

author: SMdude
author_rank: Frequent Contributor
timestamp: August 23, 2018, 07:39:48 am
content: I think you nailed it with bcr119.Check page 10 of the datasheet, it has a breakdown of the smd code..https://www.infineon.com/dgdl/Infineon-BCR119SERIES-DS-v01_01-en.pdf?fileId=db3a30431428a37301143f643b380286Cheers

author: Garywoo
author_rank: Contributor
timestamp: August 23, 2018, 08:07:16 am
content: Nice find SMdude!I was a little unsure about the max collector current of 100mA with the bcr119, as that seemed a little low to me, so I was leaning towards the 2N7002 which comes in variants from 115mA to 1.4A.

author: SMdude
author_rank: Frequent Contributor
timestamp: August 23, 2018, 10:48:03 am
content: If you're ever unsure, pop an ammeter in and see what current the load draws, then it will be easier to sleep at night!

author: Garywoo
author_rank: Contributor
timestamp: August 24, 2018, 01:07:50 am
content: I tested the current between one channel of the LEDs and the transistor, and read 315mA at full brightness.As I mentioned, the BCR119 has a max collector current of 100mA. It's looking unlikely that it's a BCR119.Does anyone else concur that it could be a 2N7002?

author: amyk
author_rank: Super Contributor
timestamp: August 24, 2018, 01:57:23 am
content: Not BCR119, nor 2N7002. If you Google pictures of those you will see why.The former has literally "WKs",like this onewhere you can just make out the marking "WKs". Not WKC.The latter does not have the "72" at vertical, and their mark is "12W". You can see themhere.Now Google "WKC sot23" and you find...this.PMV20ENR. You will also find some other people asking what this part is, on the same LED strip as yours (a Philips Hue lightstrip, I presume?) with the same conclusion:https://www.mikrocontroller.net/topic/443091http://elektronikforumet.com/forum/viewtopic.php?f=8&t=91868Philips/NXP/Nexperia are known to use the 3-letters + vertical date/batch code scheme.Here's a previous repair thread with a board full of them.

author: Garywoo
author_rank: Contributor
timestamp: August 24, 2018, 01:38:52 pm
content: Fantastic info, thanks so much amyk!You are right about it being from a Philips Hue Lightstrip.PMV20ENR looks to be a good match.In that second forum link. I saw a suggestion ofIRFML8244TRPbFas an alternative. They are a little cheaper, and since I have a number of PCBs to repair, and require ~50, it's a decent saving. Is this a sensible alternative?

author: Garywoo
author_rank: Contributor
timestamp: August 30, 2018, 10:56:40 am
content: Ended up purchasing the PMV20ENR's. They worked perfectly.Thanks again for the help!