Cheap (shit quality) laptop power supplies question - Page 1
Forum section: electronics / projects

author: Hagis2k
author_rank: Regular Contributor
timestamp: February 07, 2015, 05:35:04 pm
content: Well i bought this cheap as charger from china and you get what you pay for lol i knew it would be bad but not this bad lol!Anyway when i got it i realised that my little mini laptops didn't like it at all the touchpad did lock up and not respond so i measured the ripplevoltage of the psu and compared it to a vanson universal charger where the china charger had voltage spikes from like 350mV-1Vpp where thevanson was like 20-28mV did test them both under load and not under load and the chinaq psu was still giving those voltage spikes so i crackedthe case open and was kind of amused no emi/rfi filters so all noise can go back to the grid and CE marking ChinaExport lolI was thinking is there any easy way to supress the spikes was thinking of voltage supression diodes or so, or do anyone else have any ideas that couldstop it from giving those spikes?Otherwise ill just buy another one a bit more expensive and hope for the best

author: dannyf
author_rank: Super Contributor
timestamp: February 07, 2015, 06:02:37 pm
content: Quotenot that bad looking actually if you think about how much the parts cost the assembly cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power supply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the way how did yousupply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the way how did you cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power supply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power supply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the way how did you way how did youknow that your touchpad worked even at this price i think you got a bargain good luck with it cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power supply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the way how did you if you take care of cost the manpower invested to produce this thing it is a miracle tat it actually worked i think for the price you paid it is a pretty good little power supply that actually provided power in other cases it would have just burned your laptop let alone your little touchpad by the way how did you it will servce you a long time

author: GreyWoolfe
author_rank: Unknown
timestamp: February 07, 2015, 08:36:54 pm
content: bad dannyf, don't encourage sentence run on.

author: elgonzo
author_rank: Unknown
timestamp: February 07, 2015, 08:43:06 pm
content: Quote from: dannyf_does_not_quote_properly on February 07, 2015, 06:02:37 pmThat's how my brain looks from the inside

author: retemitlum
author_rank: Newbie
timestamp: February 08, 2015, 12:49:51 am
content: Fixed it for you dannyf :"Not that bad looking actually.If you think about how much the parts cost, the assembly cost, the manpower invested to produce this thing. It is a miracle that it actually worked.I think for the price you paid, it is a pretty good little power supply, that actually provided power.In other cases it would have just burned your laptop, let alone your little touchpad.By the way, how did you know that your touchpad worked ?Even at this price, I think you got a bargain.Good luck with it, it will service you a long time."

author: cpt.charlie
author_rank: Contributor
timestamp: February 08, 2015, 01:14:45 am
content: I have seen this problem a few times before, always in Asus eeepc with cheap Chinese adapters without earth connection, however with other cheap adapters that have earth connection the touchpad works well.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 08, 2015, 01:18:02 am
content: It appears to be "RHOS" compliant. I think that it means there is less lead than usual?

author: SeanB
author_rank: Super Contributor
timestamp: February 08, 2015, 08:14:48 am
content: In this case ROHS means Removal Of Highly expensive Specs.Fake capacitors that probably have half the rating, and with a life that might not make 100 hours. You could remove the spikes by replacing the 2 output capacitors with real ones, and it would work well then.

author: Hagis2k
author_rank: Regular Contributor
timestamp: February 08, 2015, 12:21:52 pm
content: In fact i did try that with two Rubycon ZLJ 1000µF 25V didn't do much at all i seen that most other real ones also uses scottky diodes in stead of normal silicon ones and they also have an inductor after the transformer and diodes anyway i decided to lower the voltage on a quality one that i have here

author: DanielS
author_rank: Frequent Contributor
timestamp: February 08, 2015, 04:47:31 pm
content: Quote from: Hagis2k on February 08, 2015, 12:21:52 pmThat depends on the power supply topology. The inductor is necessary in voltage-fed converters but optional in current-fed ones where the primary-side buck inductor provides lumped inductance for the outputs.In this case though, neither appears to be present. The film cap across the transformer's primary might hint at a resonant converter.The voltage spike on that scope screen-cap appear to be under 10µS in duration. OP would need to go down there and take a look at what the switching noise really looks like.

author: Mark
author_rank: Frequent Contributor
timestamp: February 08, 2015, 07:02:57 pm
content: Quote from: rx8pilot on February 08, 2015, 01:18:02 amLess laed than usual.