Bad/leaky cap?

[ipman]

Found this Lelon cap on the interface board of a LG W1934S monitor.
The vent is covered with a redish thing and it's ESR is looking unusually: 0.36 ohms compared to another ones which are 0.13-0.16ohms.
It's a Lelon branded 220uF/10V cap.
Do you think this is a bad cap? Or a measurement error (altough I tested it more than 4 times).

[PCBONEZ]

Re: Bad/leaky cap?

Looks like ink to me.
Sometimes they mark caps as part of QA so they know some check or another got done.
.

[ipman]

Re: Bad/leaky cap?

There's no other cap on that board marked as such.
But yes, maybe ink.
My feeling is that I should change it, based on the reputation of Lelon brand, but I wanted a second opinion.
I will remove it and measure the capacity also, ESR looks a bit weird when measured on-circuit.
Anyway, never seen such a small cap failing. It's filtering a 5V line to a regulator, but is behind another bigger cap located on power board, this one being a 1000uF/10V low-esr according to manual.

[PCBONEZ]

Re: Bad/leaky cap?

Look up what the ESR should be.
Might not even be a low ESR cap.
.
If the others you measured are in parallel and you measured in-circuit it's the other readings that are off.
.

[Agent24]

Re: Bad/leaky cap?

That red colour doesn't look like electrolyte to me... it normally ranges from brown to yellow as far as I know.

[PCBONEZ]

Re: Bad/leaky cap?

... it normally ranges from brown to yellow as far as I know.

Except for Sacon FZ which leak what looks like Shredded Wheat.
[And it probably is.....]
.

[Agent24]

Re: Bad/leaky cap?

That was a crackup! and it's funny because it's so true...

Maybe they were trying to make some alcohol from their shredded wheat, failed, and decided to use it for capacitors instead?

[ipman]

Re: Bad/leaky cap?

Today I've removed it from PCB. Now it shows values of 0.28 and slowly incresing with time. Afther just a few seconds it shows 0.31. Also, capacity measured with a multimeter (Fluke 189) is at first reading 220uF and slowly decreasing with time, in a few seconds is 213uF. Never seen that behaviour.
Indeed, it's not lowESR type, just a standard cap. It's a 220uF/10V Lelon RGA series. But they do not specify ESR at all in the datasheet, unfortunatelly.
There is no other cap in parallel.
Two more pictures of the removed cap.

[PCBONEZ]

Re: Bad/leaky cap?

There is no other cap in parallel.

I was talking about when you measured the other caps you are comparing it to.

Your measurements say the cap is fine.
.

[ipman]

Re: Bad/leaky cap?

The caps used as comparation were out of circuit, spare ones salvaged from various other electronic devices. Unfortunatelly, they are phisically bigger than this one, so they don't fit on it's place.
I will put it back, thank you.

[severach]

Re: Bad/leaky cap?

Now it shows values of 0.28 and slowly incresing with time.

You warmed it up with the solder gun. ESR goes up as it cools.

[ipman]

Re: Bad/leaky cap?

The cap was removed, allowed enough time to rest and then measured.
It was more than 1/2 hour between removal and measurement, so I think this interval is long enough.
Anyway, measured afther some time (hours) it shows the same behaviour.

[PCBONEZ]

Re: Bad/leaky cap?

Dude, it takes a few seconds for a meter reading to stabilize.
That's true of most all meters.
.
There is no current flow trough the leads then you attach the meter initiating current flow through the meter and leads.
Current is electron MOVEMENT. There is a TIME factor in any movement.

Do you really expect all the circuits in the meter it to be -instantly- stable and at nominal values the -instant- you connect it?
Electricity doesn't work like that.

A $200-$1000 ESR meter might stabilize fast enough you wouldn't notice the change but probably not even then.
.
.

[ipman]

Re: Bad/leaky cap?

True for ESR.
But the Fluke meter is spot-on for most of measurements (capacitance). Tried with several caps. Altough a few microfarads cannot make a signifiant difference.
Sure, comparing a Fluke which cost hundreds of dollars, measuring quite a few times per second, calibrated against standards with an microcontroller-based ESR meter is not fair.

[ipman]

Re: Bad/leaky cap?

I've put that one back on the PCB were it belong.
It seems to be working, the weird problem was a bad contact in a lamp pigtail connector.