Faulty generic 5V 2A AC adaptor ('wall wart')

[tiff_lee]

Hi all,

i've got a faulty 5V 2A ac adaptor and was just looking for some pointers to identify the problem, sure I could buy another one for next to nothing but i'd rather try and fix it if only for the learning experience.

Here are some pics:




Output voltage was approx 5.3V but as soon as I connected a load (only had a 6 Ohm 50W resistor to hand) the voltage dropped to 1V even though the load current at that resistance is less than half what it should be capable of.
Given the complex PSUs some of you work on no doubt this is childsplay for many so please be nice!

cheers, Lee

[ReeceyBurger123]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Probably bad caps causing the fault, do you have an esr meter to check the caps ?

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Unfortunately not only a Uni-T multi meter.

Any recommendations for one? I see plenty of cheap ones on ebay but when I searched previously I recall people saying they were not 'true' ESR meters or something?

Edit: Now reading some older threads on here regarding the ebay ESR meters

[eccerr0r]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Without an ESR meter, I'd start with replacing C2 then the output caps.

[CapLeaker]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

change three caps (starting cap next to the PWM, and the 2 on the output) and be done with it.

[Dumah Brazorf]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Change the keyboard too. It looks horrible!

[momaka]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Am I the only one that doesn't see any pictures?

[stj]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

no, i dont either.

[kaboom]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

photofucket, aka M$, strikes again.

Uploaded/attached to the thread:



That said, I'd just as soon crush this thing, for obvious reasons.

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

Photobucket links dont work here? I could see them in the post ok?

[stj]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

i like that supply, it's simple and clean - even has a pi filter.

i would just replace the 3 low voltage caps with panasonic FR's and be happy.
i know it doesnt have an input choke or anything, but who cares - it's tiny.

[stj]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

oh yea, wash that keyboard!

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

ha yeah.. I think the keyboard needs burning tbh

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

So just for closure, I replaced all the caps and now it works again as it should.

I did order one of those ESR meters from ebay so once that gets here ill check the old caps just to see which one actually failed.

Cheers for the help.

[cyjun1990]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

wow! congrats...

[sam_sam_sam]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

If I buy any switching power supply I change cap on site if they are NOT well know good brand name caps
This is a 5 volts @ 5 amp power supply
It had some green colored sleeve that had printed " Low ESR " on them no brand name
I know this a hack job how ever it had 2200uf@10 volt caps were 12mm Dia and 17mm tall
It end up with a 10mm Dia and 30mm tall
It had three of them and one that was 1000uf@10 Volts 8mm Dia and 15mm tall it end with a 8mm Dia and 20mm tall
I could NOT find any with that size at Digikey I look for some time so I did a hack job on the case
I would use KY,KME,FC or FR

[zx8401]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

LOL i do like your easy access to the capacitors

You can keep an eye on the tops for bloating or leakage, it reminds me of the valve amplifiers that proudly show the valves sticking out of the case.
Makes it more expensive you know

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

ESR meter arrived today, one of the 470uF caps had a value of 117uF and ESR of 39Ω

[stj]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

which meter did you get?

[tiff_lee]

Re: Faulty generic 5V 2A AC adaptor ('wall wart')

I actually ordered 2, this one
http://www.ebay.com.au/itm/291601505...%3AMEBIDX%3AIT

and the diy kit with rotary encoder
http://www.ebay.com.au/itm/301837290...%3AMEBIDX%3AIT

I recall reading though your thread modding your own, some top tinkering