LED lighting blowing it's fuse (solved!) - Page 1
Forum section: electronics / repair

author: Brad808
author_rank: Contributor
timestamp: February 11, 2023, 12:47:10 am
content: I have some LED warehouse lighting (http://rabdesign.ca/wp-content/uploads/RAB_SpecSheet_RHB1R-LED150_2019-1.pdf) that died during a power outage. I've opened up the driver circuit for them and (after removing a bunch of potting compound) I was able to get to the fuse, which was blown. After replacing the fuse I powered it up with a series bulb and unfortunately I still have a short circuit somewhere. That's about as far as I've gotten so far but I have 5x of the units so I'd like to track down what the problem is (hopefully they all have the same fault). This is out of my range of knowledge though so any help is appreciated. Any good starting places for troubleshooting this fault?Here are a few pics. I know they aren't great and I can upload more as I continue to remove the epoxy to expose the components I just figured I would get a head start on some troubleshooting help because I know I'll need ithttps://photos.app.goo.gl/cSXRbwSbTyCLnoru8

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2023, 12:52:57 am
content: That's expected, fuses generally don't just blow. The fact that it's potted greatly increase the difficulty level here but it's not impossible. You're going to have to start measuring and determine what parts are shorted. I would expect the chopper transistor is dead, and probably the IC that drives it. The bridge rectifier may be shorted too but they are pretty robust.

author: thm_w
author_rank: Super Contributor
timestamp: February 11, 2023, 01:31:57 am
content: Agree with james, on the heatsink you can see a large black package, probably the rectifier. Then to the right of that likely the main switching transistor.Measure those two, bridge rectifier with diode mode on your meter.Transistor, maybe check the resistance between pins.Could also check the MOVs (blue packages).But its going to be a pain in the ass with all that potting. Apparently there isthis stuff.You might want to look around for the cost of a replacement driver. I see some 150W 48V units for $50, but didnt look further.Also for future, maybe adding additional surge protectors would help?

author: Brad808
author_rank: Contributor
timestamp: February 11, 2023, 01:57:34 am
content: Thanks for the help. I've uncovered the transistor to the right of the bridge rectifier. I believe it is:https://datasheetspdf.com/pdf/1273460/NCEPowerSemiconductor/NCE70T360F/1The farthest from the bridge rectifier is:https://datasheetspdf.com/pdf/1272427/WON-TOP/ER806F/1I think I will start by pulling the one closest to the bridge rectifier and see how it tests. EDIT: Yes appears to be deadhttps://photos.app.goo.gl/6C3hYGiVFXEoQTHx7Yes the potting compound is a pain, but I'm hoping if I figure out the problem on one then I'll be able to skip right to that section on the remaining lights and avoid removing 90% of it.The lights themselves are from my work and were being tossed so they are free to me. I won't be out anything or too hurt if I can't get them going. I just figured I could hopefully save some stuff from going to scrap.

author: Brad808
author_rank: Contributor
timestamp: February 11, 2023, 03:44:48 pm
content: So I'm looking at this again today. I've removed the chopper transistor and the short goes away. I was able to verify the bridge rectifier is good.https://photos.app.goo.gl/gzyKw6naB8mX1wS87I want to verify the controller IC before ordering parts but I'm getting stuck. On the back of the PCB I can only see 2 ICs. IC1 shows continuity from pin 4 to pin 3 of the chopper and around 67ohms of resistance between pin 5 to pin 1 of the chopper. IC 2 doens't seem to be connected in any way to it so I'm assuming IC1 is probably the controller IC for it? Part number for IC1 is BQDBQA, I wasn't able to find a datasheet for it. I checked another one of the LED lamps and IC1 is a different part number BQDBPA, also couldn't find any datasheet.Any ideas how I can test the controller IC and/or find a suitable replacement? Thanks

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2023, 06:41:31 pm
content: That's not a part number for an IC, at least not like one I've ever seen, it's possible that it's a house numbered part, or a coded number on a small SMT package. If you can't identify the IC you might be screwed, unless you want to chance it and try installing a new transistor but I think it is unlikely that the IC survived. You might find a match by comparing the pinout to various LED driver ICs in that package style.

author: fzabkar
author_rank: Super Contributor
timestamp: February 11, 2023, 07:13:37 pm
content: Quote from: Brad808 on February 11, 2023, 03:44:48 pmSY5882A, Silergy, Single Stage Flyback and PFC Controller with Primary Side Control for LED Lighting and Multiple Dimming Mode Options, marking BQDxyz, SO8:https://datasheet.lcsc.com/lcsc/1912111437_Silergy-Corp-SY5882AFAC_C365711.pdfThis is a similar, earlier version of the IC (SY5882):SY5882, Silergy, Single Stage Flyback and PFC Controller with Primary Side Control for LED Lighting and Multiple Dimming Mode Options, marking BCIxyz, SO8:https://datasheet.lcsc.com/lcsc/1810191210_Silergy-Corp-SY5882FAC_C125902.pdf

author: Brad808
author_rank: Contributor
timestamp: March 11, 2023, 01:35:45 pm
content: Just to conclude this I received the parts earlier this week and managed to fix all 5x lights. All 5x had the same fault; blown chopper transistor and blown fuse. I didn't order the controller ICs because after going over the datasheet I couldn't find any obvious faults with them, I figured I'd take a chance with just the chopper transistor and thankfully that was all it was. The potting compound was a pain, but after the first one I had a reference to go off so I only needed to remove what was needed for all the rest and it didn't take so long (about 45 mins to take apart, fix, put back together each light).Thanks for all the help!https://photos.app.goo.gl/4fpimuN12P9wj6qi8

author: james_s
author_rank: Super Contributor
timestamp: March 12, 2023, 03:02:51 am
content: Nice job, that's an impressive repair.