EEVblog #765 - LED Panel Lighting Switching Noise

[DutchGert]

+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 !

[LordNobady]

+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.

[Fungus]

+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.

[station240]

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.

[EEVblog]

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.

[EEVblog]

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.

[EEVblog]

Have you ever tried to open one?

Yes, many times.

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.

[Corporate666]

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.

[Monkeh]

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.

[f4eru]

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

[David_AVD]

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.

[Kjelt]

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