Anyway i thought i share the problems i had with a cheap chinese power supply i did buy:
I was in need for a power supply for my small Sony netbook style mini laptop,
so i bought one that i thought should be "decent" but buying from china is like a lottery lol!
So anyway i got the power supply like a week ago and when i plugged it in the little laptop started behaving very strangely locking up touchpad not responding so i was like wtf now i unplugged the new psu.
And the laptop started working like normal so then i just decided to look how the dc voltage looks like grabbed the oscilloscope and i was a bit shocked at first glance i thought i did something wrong when i measured it was just WAY to much spikes and noise:
But it gave me spiked and noise like mad i even tried changing the capacitors on the secondary side without any change so i gave up was thinking of putting an inductor between the capacitors on the output to try to suppress the spikes.
No input filter emi/rfi poorly built and since i don't own a insulation transformer at the moment but i shall wind one my self soon, i didn't feel for measuring the noise on the switch transistor probably that one who causes it shall save the unit until later and play with it a bit.
Some pictures of the power supply:
Notice the RHOS text hahaha chinese people they can clone anything
I quickly sketched up the secondary side for fun c10/c11 are not 3nF but the rest of the values should be correct.
So anyway i did crack another laptop charger open and took it a part looking around in the circuit and i found a voltage divider
that at 19V left pin2 with 2.5V so i did some basic calculations and figured out that if i place a 14K resistor on R60 place:
R60 is 16.5Kohm here
R60 changed to 14Kohm
Changed the capacitors as well (and lol i see the little hole in the solder on one cap i fixed it after the pic was taken. same with the cables)
So at last correct voltage 0.26V over what i did calculate so not to bad and the laptop is happy now
So this did work now i have a power supply that feeds 16.76V out instead of 19V changed the cable and now everything works just fine.
So cheap chinese power supplies can be both win / fail lol
I was in need for a power supply for my small Sony netbook style mini laptop,
so i bought one that i thought should be "decent" but buying from china is like a lottery lol!
So anyway i got the power supply like a week ago and when i plugged it in the little laptop started behaving very strangely locking up touchpad not responding so i was like wtf now i unplugged the new psu.
And the laptop started working like normal so then i just decided to look how the dc voltage looks like grabbed the oscilloscope and i was a bit shocked at first glance i thought i did something wrong when i measured it was just WAY to much spikes and noise:
But it gave me spiked and noise like mad i even tried changing the capacitors on the secondary side without any change so i gave up was thinking of putting an inductor between the capacitors on the output to try to suppress the spikes.
No input filter emi/rfi poorly built and since i don't own a insulation transformer at the moment but i shall wind one my self soon, i didn't feel for measuring the noise on the switch transistor probably that one who causes it shall save the unit until later and play with it a bit.
Some pictures of the power supply:
Notice the RHOS text hahaha chinese people they can clone anything
I quickly sketched up the secondary side for fun c10/c11 are not 3nF but the rest of the values should be correct.
So anyway i did crack another laptop charger open and took it a part looking around in the circuit and i found a voltage divider
that at 19V left pin2 with 2.5V so i did some basic calculations and figured out that if i place a 14K resistor on R60 place:R60 is 16.5Kohm here
R60 changed to 14Kohm
Changed the capacitors as well (and lol i see the little hole in the solder on one cap i fixed it after the pic was taken. same with the cables)
So at last correct voltage 0.26V over what i did calculate so not to bad and the laptop is happy now
So this did work now i have a power supply that feeds 16.76V out instead of 19V changed the cable and now everything works just fine.
So cheap chinese power supplies can be both win / fail lol
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