Is it okay to replace 1/2 watt resistor with 1 watt resistor in AC/DC adapter?

[chth96]

I have purchased an 100-240v AC/5v 2a DC adaptor from aliexpress,and a month ago It smelled burning when I plugin it powerstrip.
Since then, This AC/DC adaptor have been out of order.
But A few days ago,I replace 0.5 watt resistor with 1 watt resistor(1ohm) in this adapter.
After replacing resistor,It succeed to recharge all of android phone.And When I measure voltage on the two pins of USB port,It shows 5.5v
Is it okay to replace 1/2 watt resistor with 1 watt resistor in AC/DC adapter?
And Is there any possibility that it will suddenly explode as well as to be out of order again?

[stj]

the resistor is intended to act as a fuse,
the fact that it failed and the psu still works is strange.
maybe it was under-rated

[redwire]

OP why did you replace this resistor? Hint: it was not the part that was burning and smelling...
It looks like 0.1Ω which needs a few amps to heat up!
Your post does not make any sense.
So I would say yes it will blow up and back to Aliexpress order another one.

[chth96]

OP why did you replace this resistor? Hint: it was not the part that was burning and smelling...
It looks like 0.1Ω which needs a few amps to heat up!
Your post does not make any sense.
So I would say yes it will blow up and back to Aliexpress order another one.

Although,I have nearly no knowledge about repairing electronic,
Just like what stj said,I also think that this 0.5 watt resistor maybe act like a fuse,and decisively I noticed that the last black band on surface of 0.5 watt resistor have been damaged.
You can confirm damaged black band from attached file(0.5 watt resistor) which I uploaded yesterday.
Of course,There is no resistor or other components which has any damage on their surface.
By the way,When I have to replace any act like fuse resistor, Should I replace this resistor with other one which have same watt as well as same ohm value?

[chth96]

the resistor is intended to act as a fuse,
the fact that it failed and the psu still works is strange.
maybe it was under-rated

when It failed and smelled burnning, I noticed that one pin of 220v male plug have been not fixed,but It swayed from side to side whenever I shaked it. So I fixed it with epoxy glue.

[stj]

use a fuseable resistor - sometimes described as a flameproof or safety resistor.
they are gray
a regular resistor with catch fire and burn the pcb!

[chth96]

use a fuseable resistor - sometimes described as a flameproof or safety resistor.
they are gray
a regular resistor with catch fire and burn the pcb!

Do it means that I should desolder 1 watt resistor(1ohm) from adaptor's pcb and look for flameproof resistor instead of normal carbon resistor like what I soldered on the pcb?

[stj]

yes,
if that one blows it will create a big mess

[redwire]

OP, this is a cheap USB charger.
It should have the right fusing to prevent house fire.
It should have a good transformer to prevent electrocution. (is this what is burning?) Check the isolation resistance between pri-sec.
It should have a TL431 IC for precise 5V regulation. Here it has a zener diode so the 5V will not be accurate.


I expect the bridge rectifier to just pop if anything goes wrong.
Still not making sense why the resistor cooked but nothing else is. Unless the prongs inside shorted to the board?

[chth96]

Thank you very much for reply!
I measured all of resistor on the pcb.
You can confirm all ohm value of resistor from the below attachment.
I think that ohm value of all resistor seems to be correct.
and I found that pcb has CSC7203,MB10M,TWS 817C 217 ic components. It seems that Burnt resistor and mb10m bridge rectifier was soldered next to wire of 220v male plug.
Is it necessary to check that mb10m bridge rectifier was broke or not?
And How can I check mb10m bridge rectifier if it was out of order?

[chth96]

I just noticed that Its current is very weak.
Whenever I use ampere app in any android phone which is connected to this AC/DC adaptor,It shows 150ma at most, While It shows 800-1200ma whenever I connect it to other AC/DC adaptor.
It must show more than 1000ma in ampere app, because It is written 5V 2A output on its cover,But It only shows 150ma!
I assume that some IC component is out of order and it hinders to supply sufficient current for output.

EDIT:I confirmed that the blue resistor(1 watt,1 ohm) ,which I replaced with, is a flame proof resistor.

[stj]

https://yt.artemislena.eu/playlist?l...vjBw_J7X_X5OnU

[petehall347]

its a cheap crap power supply that can not do what is says on the sticker . . i got burned with one .reported it to trading standards but they didnt do anything

[redwire]

I say this charger does not have a TL431 so it has poor voltage regulation and is too cheap.
People buy $600 smartphones and then want to use a $2 chinese charger that can be a fake, it has defective output. I hope the transformer windings will not kill someone.

So the fusible resistor popped due to a short-circuit between the board and the mains input wiring? Or did this junk ever work?
Check for an open diode in the MB10 bridge rectifier, there are 4 diodes inside to test. But these parts usually burn up or explode if they see an overload. So I wonder if this cheap charger ever really worked.

[chth96]

I checked MB10M with LCR-T4,You can confirm all of results from the below attachment.
As Hioki Card Hi Tester 3240 is the only multimeter currently I have ,It is impossible for me to check it with reverse polar test for diode.

[redwire]

The bridge rectifier tests looks OK. Low HV bus voltage only if a diode inside is open. If a diode inside shorts the whole bridge blows up.

You had smoke and sparks so it's hard to tell what is damaged. Is it 5.0V but just weak, collapses with small load? What is the output voltage now.
I would make sure C2 is good. Make sure the transformer core is not broken, cracked or glue came apart.
Otherwise I would suspect the transformer primary windings are cooked due to the short or maybe the IC is bad.

But for the $25 of your life you waste trying to fix it, maybe just buy something new?

[chth96]

I tried to measure voltage of transformer by placing test lead of multimeter on soldering point of transformer.
In order to measure voltage which came from 220v plug and flow into transformer, I pluged this AC/DC adaptor in power strips and I set multimeter to AC voltage mode and placed black and red lead on the point where I draw black and red arrow in the attachment picture.
But as soon as I placed black and red lead,I saw strong sparks and shrapnel of CSC7203 pop up and it brushed past my eyes and hit my hair.
Since then, whenever I touched some soldering point in the bottom of PCB, I felt strong electronic shocks..
So I dispose of this chinese AC/DC adaptor,But Now I am worried that it is safe to keep using power strips in which I pluged blown up AC/DC adaptor.

[stj]

lol
you cant use a voltmeter on the transformer - it's driven at 20-60KHz with about 340v

[petehall347]

whenever I touched some soldering point in the bottom of PCB, I felt strong electronic shocks..
.