bad caps story: wifi access point

[eccerr0r]

I had a D-link 802.11b+ access point for many years, but since it worked I never felt like disposing of it. I really should... alas I found a use for it - I hooked it up to my pfSense router box and used it as a captive portal public wifi access point.

Until it stopped working. It had been very flaky for a few months before the point it would stop responding.

At first PSUs tend to be the things that die first, alas when I tried a different wall wart, no dice - same behaviour. So curiously I pulled it open since I now have a smt rework station that's waiting to gut things. There are no caps that were bloated, the biggest ones looked perfectly fine.

I guess this is the end for this 802.11b+ access point, time to toss into the spare parts pile, but something told me to use my ESR meter. The big caps looked just fine, however found three of the five tiny through hole 10uF electrolytics that were over 5 ohms. Red flag! So I soldered a 10uF cap in parallel to the bad ones on the bottom side of the board.

The access point came back to life!

Now it gets put back into service, and let's see how long this lasts...

Question now is whether or not I will actually clean up the bodgey fix (like that radio...) alas this device will never be an antique...

[goontron]

Re: bad caps story: wifi access point

B? jeez, im running 5GHz N!

[stj]

Re: bad caps story: wifi access point

Question now is whether or not I will actually clean up the bodgey fix (like that radio...) alas this device will never be an antique...

i have a 10/100 8way hub that failed last month.
similar story.

i didnt want to open it again - it exists out of sight.
so i replaced all the 10uf electrolytics with salvaged surface-mount ceramics,
and replaced a pair of 100uf electrolytics that were in parallel to get the esr down with a single 180uf poly i also pulled from something else.

[eccerr0r]

Re: bad caps story: wifi access point

Yup, I used salvaged caps scavenged from something else and stuck in my parts bin. These were also aluminum electrolytics so still cheap repair...

I was about to also make a posting about surface mount ceramics - I was surprised when I tested one that I pulled, it was 10 freaking microfarads. How high do they go? I thought that you could only get that high with tantalum or aluminum electrolytic, else it'd have to be huge.

Now voltage rating I have no idea...

[stj]

Re: bad caps story: wifi access point

how high?
high.
220uf atleast.

[stj]

Re: bad caps story: wifi access point

datasheet

[eccerr0r]

Re: bad caps story: wifi access point

Interesting. Now I wonder how much they cost compared to aluminum electrolytics

Back on topic, the caps that died, they're ~ 4.2mmx8mm and the brand name is "Stone" ... and now that I have three of these little tiny caps go belly up, are these less reliable than larger 5mm caps (which really aren't that much more reliable...)

My jar of bad and unwanted parts is filling up... at least these caps don't take much space...

[stj]

Re: bad caps story: wifi access point

life is often directly related to can size.
one of the reasons i hate smd electrolytics!

[eccerr0r]

Re: bad caps story: wifi access point

For the heck of it, I ended up replacing two of the caps, the third one I left with the parallel cap on the bottom. The first one I pulled out was the easiest, it just came out. The second one I had to deal with a ground plane. Ouch...that was REALLY hard to remove. I finally got it out using my 100W/140W solder gun in 140W mode.
The third one was underneath a socket and I didn't feel like removing that socket to get the cap out after fighting that ground plane...
I used 5.2mm caps but had to bend them over to make them clear the plastic on top.

[stj]

Re: bad caps story: wifi access point

i used ceramics because they sit perfectly between the original pads!

[eccerr0r]

Re: bad caps story: wifi access point

Hmm...the 10uF ceramic SMT that I harvested from a board seem a bit too large to sit between the pads of a 4 or 5mm cap?
Maybe I have an older one, not sure... Now the 220uF ceramics I have to see...

[kaboom]

Re: bad caps story: wifi access point

brand name is "Stone" ...

Low end shit from the bad old days of the first winmodems, soyo motherboards/end of the "fake cache" era, those early 5 channel sound cards that never worked right, and buggy via chipsets.


One of the original "plague" caps... IOW, bad even for smt lytics.