Author Topic: EEVblog #765 - LED Panel Lighting Switching Noise  (Read 16650 times)

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Offline DutchGert

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #25 on: July 14, 2015, 09:09:51 am »
+1 for the teadown and further investigation. Please show us the indside of this device.
+2.  Have Dave2 fish it out of the trash and lets find out why its different than the others.
+3 Please make a follow-up video showing us the insides of that crappy power supply. This should be very educational of how not to build a power supply.

Yes pleasw :)!
 

Offline LordNobady

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #26 on: July 14, 2015, 09:23:36 am »
+1 for the teadown and further investigation. Please show us the indside of this device.
+2.  Have Dave2 fish it out of the trash and lets find out why its different than the others.
+3 Please make a follow-up video showing us the insides of that crappy power supply. This should be very educational of how not to build a power supply.

Yes pleasw :)!

an other cap replacement video? no thanks.
Or make it something special.
 

Offline Fungus

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #27 on: July 14, 2015, 10:38:31 am »
+1 for the teadown and further investigation. Please show us the indside of this device.
+2.  Have Dave2 fish it out of the trash and lets find out why its different than the others.
+3 Please make a follow-up video showing us the insides of that crappy power supply. This should be very educational of how not to build a power supply.
Yes pleasw :)!
The internal design might actually be OK. It could just be the bad soldering, cheap-ass caps and general penny-pinching manufacturing that's letting it down.

That would only be a 2-minute video though.

And if it's potted...? Forget it. Simply not worth the effort. There's a thousand examples of that sort of manufacturing out there.


 

Offline station240

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #28 on: July 14, 2015, 01:49:33 pm »
At best that duff PSU would be a 2 minute tear down, 10 seconds of smashing it with a hammer, 1:50 of talking about all the things wrong with the PCB extracted.
 

Offline EEVblog

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #29 on: July 14, 2015, 01:54:49 pm »
PS. If it is potted then maybe it isn't worth it.

Almost certainly not potted. Just needs a messy dremel to open the welded seems. maybe can be cracked open by force, but I've never had much luck with that.
 

Offline EEVblog

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #30 on: July 14, 2015, 01:58:54 pm »
Dave, why did you use an oscilloscope rather than a spectrum analyzer to look for interference from the switching power supplies?
It was the first instrument available that could still show the issue during a quick video shooting?

a) Everyone has a scope. Not everyone has a spectrum analyser. They can't play along at home.
b) It's most common to see noise like this when measuring stuff on a scope, so it's much more relevant and meaningful to people's everyday measurements, and I think easier for people to relate and understand.
c) I've done a previous video explaining this that used a scope, so it ties in.
d) Noise measurements (particularly PSU rail noise) are done with scopes with a 20MHz bandwidth limit.

I shot some extra spectrum analyser stuff today with the remotes.
« Last Edit: July 14, 2015, 02:04:29 pm by EEVblog »
 

Offline EEVblog

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #31 on: July 14, 2015, 02:04:12 pm »
Have you ever tried to open one?

Yes, many times.

Quote
It's pretty difficult, but there are videos of people doing it without completely wrecking the enclosure in the process. Basically hit the side with a hammer, shatter the glue.

IME they are usually ultrasonically welded, not glued.
 

Offline Corporate666

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #32 on: July 14, 2015, 04:34:09 pm »
an other cap replacement video? no thanks.
Or make it something special.

I was thinking a 2 minute teardown.  It's not an especially interesting circuit or device, but what is interesting is why one is so noisy and the others aren't.  IIRC, wasn't Dave having noise issues from day one with those lights? 

I am mostly curious to see whether the unit had a failure and they just shipped it anyway (no testing), or whether the right parts were even installed in the first place.  There is a video out there of a guy tearing down Li-Ion cells and finding some of them filled with salt/baking powder.  It's very interesting to see the depths some of these no-name Chinese manufacturers will sink to.  There could be a goldmine of hilarity inside that power supply.
It's not always the most popular person who gets the job done.
 

Online Monkeh

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #33 on: July 14, 2015, 06:15:45 pm »
PS. If it is potted then maybe it isn't worth it.

Almost certainly not potted. Just needs a messy dremel to open the welded seems. maybe can be cracked open by force, but I've never had much luck with that.

Vice works a treat on traditionally shaped ones.
 

Offline f4eru

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #34 on: July 14, 2015, 07:07:19 pm »
A dumb idea : you can test ther ESR of the output caps by putting the ESR meter on the output wires, without opening the darn thing :)
Could be a standard test for PSUs :)

Offline David_AVD

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #35 on: July 14, 2015, 09:01:28 pm »
Vice works a treat on traditionally shaped ones.

+1 on that.  You can hear the crack as the two halves let go.  Sometimes you need to reposition the case in the vice a couple of times.

If you don't want to reassemble the unit you can be less careful and loose some plastic in the process.
 

Offline Kjelt

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Re: EEVblog #765 - LED Panel Lighting Switching Noise
« Reply #36 on: July 17, 2015, 08:54:03 am »
I always use an iron saw on all sides, if it doesn't matter that you saw a bit through some elco's since you're gonna throw it away anyhow it is much easier  :)
 


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