EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: bratboy on April 09, 2021, 09:11:50 pm
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Hi there, I have a question about a corn light I have. I picked it up and opened it and there was a 22 microfarad capacitor that blew up. I'm thinking that's the only thing I need to repair. It's an epoxy. Anybody have any advice on how I can get in there and replace it? I'm not an expert Electronics guy, I'm very basic but I've done repairs in the past.
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Scratch away if you can, you need to remove enough grey stuff, then find the right polarity.
If you're not used to electronics though I'd consider this a hazardous waste of time.
I'm used to electronics and don't bother repairing single "bulb" assemblies...
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Hazardous in what way? It did have a polarized capacitor but I understand you can replace it with a non polarized. Is that right? The thing knocks out a lot of light so I might as well try to make a repair.
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Hazardous because it's partly or entirely mains referenced. A waste of time because with a failure that violent I'd expect that's a symptom of another, potted, problem.
If this is a ESR sensitive position (again, potting in the way to reverse engineer) a NP cap may not survive.
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22uF sounds like the main reservoir cap, probably rated 400V. The fact that it exploded suggests you might want o see what caused that first, or the replacement may do the same.
I've not heard of the term "cornlight" before - I guess this is "COB on the corn"...? :-DD
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It's a 50v and yeah cob on a corn sounds right!
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The cap could have failed due to poor design, cheap manufacturing, heat stress, over voltage, water ingress or a lightning strike. It's anyone's guess, but LED bulb failures are often less catastrophic than this.
The LEDs may have failed too. Test the strips with a diode meter or low voltage DC source.
Seriously, trash the mains PSU part and keep the LED arrays as they might be usefull for some other project using a safe and proven DC supply.
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50v is not the mains reservoir cap, but probably output smoothing, in which case the cause of failure is likely the LED string went open-circuit, causing the constant-current driver to raise its output voltage to the max and exceeded the 50v.
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If it wasn't potted I'd say it's a reasonably easy repair, but potted adds a huge amount of labor and difficulty. If I really wanted to salvage something I think I'd cut off the existing driver and wire the LED part to a different driver.