Can you identify this diode? - Page 1
Forum section: electronics / repair

author: salomonander
author_rank: Regular Contributor
timestamp: August 11, 2025, 11:44:17 pm
content: Hey there,can anyone make out what D5 is? It sits in a smps. Thanks!

author: salomonander
author_rank: Regular Contributor
timestamp: August 11, 2025, 11:54:50 pm
content: Also D4I want to replace all those badly soldered parts

author: langwadt
author_rank: Super Contributor
timestamp: August 12, 2025, 12:09:08 am
content: so there is nothing wrong with them, then why replace them? some solder wick to clean up the soldering if you really must

author: coromonadalix
author_rank: Super Contributor
timestamp: August 12, 2025, 12:15:05 am
content: find the ic part number and check it's aplication note it will give you some ideas

author: salomonander
author_rank: Regular Contributor
timestamp: August 12, 2025, 12:42:09 am
content: Thanks guys, problem is i cannot read whats printed on there. Can you?I want to replace them as the unit has some oscillating issues and since i have no schematic,I guess replacing these badly hand soldered parts is my best first bet.

author: fzabkar
author_rank: Super Contributor
timestamp: August 12, 2025, 03:47:30 am
content: Quote from: salomonander on August 12, 2025, 12:42:09 amAs already suggested, examine the application circuits on page 10 of the datasheet:https://www.st.com/resource/en/datasheet/l6562.pdfD5 will be an ultrafast rectifier.This is the one in the app cct:https://www.st.com/resource/en/datasheet/stth1l06.pdf

author: gamalot
author_rank: Super Contributor
timestamp: August 12, 2025, 12:14:08 pm
content: Quote from: fzabkar on August 12, 2025, 03:47:30 amThe picture is too blurry to see clearly, my guess is STTH1R06Ahttps://www.st.com/resource/en/datasheet/stth1r06.pdf

author: Haenk
author_rank: Super Contributor
timestamp: August 12, 2025, 01:05:07 pm
content: I don't see a reason to replace them, just because of the solder blob. A quick continuity test should be good enough.Maybe check C17, there might be a crack visible? (Or might be just debris...)Maybe check soldering of the components, and touch them up anyway (looks like they had problems with the quality of the solder joints).Electrolytics a worth a check, too.Edit: Check R39 - looks like a cracked solder joint; C19 does not look great, too

author: MAS3
author_rank: Regular Contributor
timestamp: August 12, 2025, 02:50:50 pm
content: If you can't read the printed text on such a part, make sure all capacitors are discharged.Take a cotton swab (i'd use my fingertip if i'm sure it's safe) and wet it with some saliva.Now swab the part, darkening that surface and create some more contrast.Take another picture before it dries out and see if that's better legible.

author: salomonander
author_rank: Regular Contributor
timestamp: August 12, 2025, 04:56:20 pm
content: Thanks a lot guys! I will reconsider replacing it. I did find some caps with high esr that i should probably replace first.

author: Kean
author_rank: Unknown
timestamp: August 12, 2025, 05:26:43 pm
content: Quote from: MAS3 on August 12, 2025, 02:50:50 pmSaliva, ick! I haven't done that for troubleshooting since I was a teenager.I'd suggest IPA, and if that doesn't work I have used a tiny amount of clear machine oil or glycerine as they are optically clear, pretty inert, and easy to clean.As the marking are usually laser engraved these days, you can also try gently rubbing with a white crayon or marker to fill the etching and then wipe clean to see if that adds contrast.

author: MAS3
author_rank: Regular Contributor
timestamp: August 12, 2025, 09:41:08 pm
content: Saliva because of being available in most cases, and last a bit longer than water before it evaporates, and much longer than IPA.Oil or glycerine will probably do better at that, but is less likely to be available.The crayon or marker tips are something i will try to remember to test in the future.