Modify a Laptop Power Supply 5V to 30V | How to make 12v to 220v inverter 

What ever be the SMPS or adaptor find TL431 has 3 pin leads, Leave the Grounded pin and one more pin connected directly to Opto coupler also leave that and the remaining pin connected to dual resistors 1st resistor (R9 in this video) one end connected with the remaining pin of TL431 and other end with ground. another VR and resistor in serious are coupled as a single resistor with o/p voltage pin. So find out easily by using multi meter at continuity checking mode and check remaining pin of TL431 and connecting resistor other end is with +o/p and another similar resistor with ground . thus these 2 resistors need to change 1 by fixed one and another by pot. thats all. After his video I have done several adapters.

I know I'm late, but maybe you still didn't find out and wonder. It's not a diode, it's the TL431, need to understand the circuit a little bit to find it by logic, it drives an opto-coupler and should be marked as "U" on the pcb, it could also be in a to92 housing or the psu work another way.

uh now I finally know why some old phones won't work while charging with one specific charger

This depends, I belive this is commonly done to enable connecting PSUs in series.

CANT 15V TO 24V (DO THIS SOME TIME BLOWING THE POWER MOSFET, YOU HAVE TO FIND 19.5V ADAPTOR

What's happening there is you are trying to over switch the ic. The so called modification here is actually increasing the duty cycle of the switching ic. You can't go beyond a specific T on.

I see there is 1 15V zener diode there, so the voltage is always a steady 15V. I removed the capacitor because the grid in my country only has 2 wires. There is no ground wire. If not remove the capacitor, when touching the output. I will receive a slight electric shock

​@@PhdHung Ah ok. Then this was only a sample schematic and this is a supply with PE on secondary -. The 2.2nF capacitor in the schematic were normally ok for touch current requirements for class II supplys. There can be some other issues if output voltage is higher then designed but this supply has apparently enought reserve for that range for normal input voltage.

The overall adapter power remains the same. If voltage increases, the current decreases and vice versa, however the max current is still the limit of the secondary winding of the transformer.

yes. Here's a cheap psu, it's very simple :D

anh thay con biến trở vô, vặn đến 24V thì rút điện, đo xem bao nhiêu ôm rồi thay bằng con trở cứng vô. nên dùng tụ 35V hoặc 50V cho an toàn anh

@@PhdHung ok ,cám ơn em, cách này hay với anh.cám ơn nhiều,he he eh

Thay con điện trở phân áp nối xuống mass thành biến trở là ok. Cái này dễ mà, bạn coi lại video có sơ đồ nguyên lý đấy.

Very difficult, you need rewinding the transformer.

capacitor that connects high voltage GND and low voltage GND. I removed it because it could cause electric shock.

@@PhdHung That's a capacitor filter. Probably to send any residual 60hz AC from the low voltage side to GND. No reason to remove it. If you're worried about shock while working on the circuit, just short each capacitor with a tool with an insulated handle and then work away.

Basically yes, aslong it uses the TL431, but need to understand the circuit to find it, also for safety, don't do something like that with electric stuff if you don't understand it, high or low voltage doesn't matter, it still can be very dangerous.

I removed the feedback voltage resistor and replaced it with potentiometer

Which and which are the value of former feedback resistor

5k

resistor 4k7 for LED :D

I have done it successfully and plenty of verity of adapters such.

Remove resistors connected to gnd. Find it near tl431

@@PhdHung All i do it is done, but if the voltage below 18V beats a sound, the more clearly audible if the voltage is lower, the led blinking, the voltage unstable, how to fix it ?

Did you removed the cap ?

I mean miler cap

here 320volt.com/en/battery-charger-with-flyback-smps-mod/

Me too

67,2 ? for what?

Thanks for watching

A trick I have found useful--look for the high-precision resisters, i.e., 4 digits for surface mount, and they are normally in the 2K-15KOhm range.

The third wire tells the laptop what charger is connected (90w 100w 120w etc) and that its a genuine charger or not

It doesn't matter, use the two wires you get 19V in between of!

when the voltage increases the current will decrease.

dell computer charger has 3 wires. +, - and PG. You can remove PG wire

@@PhdHung i got an HP one and it also has 3 wires (i don't want to kill it anyway i need it for the computer because the third wire tells the laptop it's not connected to any random power supply and if there is none it doesn't work so i can't use any charger! #SAD )

Of course

@@PhdHung no, probably not! You have to change the output diode and use a diode that can handle a higher peak!

If the resistance is large, the voltage increases

@@PhdHung depends on which feedback resistor you change as there are at least two of them in a divider bridge!

thanks bro

post photos to Facebook group, everyone will help you

Marlon Diego in that case you remove the overvoltage protection if it has some integrated chip for the working proces just diseable the pin for that and its done an if it isnt with a chip just short the two legs on the optocoupler on the primary side

I thought he'll modify PWM ;) signal and not a potentiometer at the output :D, an odd way to do it IMHO ;).

VR 10K

Thanks

Pls post pictures on FB group

@@PhdHung fb page name???

cái này dễ mod lắm anh

@@PhdHung anh mở 1 cục sạc asus thấy không giống cái của em....nhưng từ từ anh mò .....chắc cũng ra ...he he he ...cám ơn em đã đăng

Yes, it caused electric shock, so I removed it.

@@PhdHung cool, then it was simply defective, then it is better replaced, since its purpose is to close the high frequency loop, where the other halve of the problem (signal noise generator) is the capacity from primary to secondary side in the transformator, this cap close this, and avoid huge radiation between prim-sec side

thanks. I know that.

Thanks bro

Check with Zener protection diode

I want to insulate between GND HV and GND LV. In my country, there is no earth wire.

@@PhdHung yeah it wont matter.... although the cap only allows microamps it can be at quite high voltage so can damage sensitive circuits and chips so can see why you would remove it

When removing it you get a lot of interference, and if you set 5V and charge a phone the touchscreen won't answer or very badly because of this interference! You need the class Y1 capacitor, and if you have no ground you can connect a 1M resistor between neutral and negative output (it will do the job but make sure it's NEUTRAL and NOT LIVE!)

I need quick reply please.. I'm going to modify 24v 2.5 A adaptor the smd feedback resistor is 1k I removed it and hope to use 5k vr but what is the resistor I must use with vr