Hello everyone, my question is how the voltage of this smps can vary, I have seen in an online store that has done the same with this model of smps
https://shopee.co.id/SMPS-DC-Adjust...pply-6v-12v-15v-20v-24v-i.44519782.5242769485
How do I connect the poteiometer?

 

The link is broken and leads to a 404 error.
For the potentiometer, you would need a schematic diagram of the board to see if this is even possible. Just because an online source claims something can be done does not mean that you can actually do it. The schematic diagram is the only way to know for sure.

 

Hello,

I have corrected the link, it should work again.

Bertus

 

It looks like the pot(?), if that is what is is, goes in place of C108. No idea what value you need or where you can find one that will fit the holes. Having a schematic seems kinda critical unless you're just messing around and don't care if it works or not.

 

This is a 12V Wall Wart (actually it's a brick) I modified to output 13.8V. This is the solder side and the symbols of the components on the other side are represented.

Located in the "Transformer" region of MY board, I found the TL431 programmable voltage reference and the voltage divider that sets the program. In MY mod, I use a 4.7KΩ resistor and a 5KΩ pot in parallel with a 1.2KΩ resistor ("1201" on the PCB). Adjusting VR502 allowed me to tune in to 13.8V. The SPDT slide switch enables me to take my mod out of circuit and return the PS to 12V.


You probably have to identify what part of your circuit controls the output. In my case it's the TL431. Changing the voltage divider network (the 1201 and the 1401 PCB resistors) will change the output. Just be sure that if you UP the voltage output your caps need to be big enough to handle it without exploding. The caps on MY board are rated for 16V.

 

This is a 12V Wall Wart (actually it's a brick) I modified to output 13.8V. This is the solder side and the symbols of the components on the other side are represented.
View attachment 225575
Located in the "Transformer" region of MY board, I found the TL431 programmable voltage reference and the voltage divider that sets the program. In MY mod, I use a 4.7KΩ resistor and a 5KΩ pot in parallel with a 1.2KΩ resistor ("1201" on the PCB). Adjusting VR502 allowed me to tune in to 13.8V. The SPDT slide switch enables me to take my mod out of circuit and return the PS to 12V.
View attachment 225576

You probably have to identify what part of your circuit controls the output. In my case it's the TL431. Changing the voltage divider network (the 1201 and the 1401 PCB resistors) will change the output. Just be sure that if you UP the voltage output your caps need to be big enough to handle it without exploding. The caps on MY board are rated for 16V.

I can't find the tl431 on my board, this board has a soft23 with a4tfl code without datasheet and I don't know if it's a diode or a transistor

 

I can't find the tl431 on my board, this board has a soft23 with a4tfl code without datasheet and I don't know if it's a diode or a transistor

IC201 is the Tl431 regulator on the trackside, with the resistors ,I've marked them in white. With the values shown 27K, 3K+820 ohms should be 20V, .

 

IC201 is the Tl431 regulator on the trackside, with the resistors ,I've marked them in white. With the values shown 27K, 3K+820 ohms should be 20V, .

View attachment 225601

I have a 10k potentiometer but the tester says it is 11k, how do I connect it? I do not speak English

 

I have a 10k potentiometer but the tester says it is 11k, how do I connect it? I do not speak English

If you want to Lower the voltage, then put the preset across the 27K resistor pads,(remove the 27k first) , this will give up upto 10V, if you need more to vary from 2.5V to 16V, then replace the preset for a 22K.

Some switchmode PSU s don't like being variable and maybe unstable and give out whining noise.
What language do you speak?

 

If you want to Lower the voltage, then put the preset across the 27K resistor pads,(remove the 27k first) , this will give up upto 10V, if you need more to vary from 2.5V to 16V, then replace the preset for a 22K.

Some switchmode PSU s don't like being variable and maybe unstable and give out whining noise.
What language do you speak?

ok I'll try, I speak Spanish

 

If you want to Lower the voltage, then put the preset across the 27K resistor pads,(remove the 27k first) , this will give up upto 10V, if you need more to vary from 2.5V to 16V, then replace the preset for a 22K.

Some switchmode PSU s don't like being variable and maybe unstable and give out whining noise.
What language do you speak?

If it works, Thanks. Originally the voltage is 24v after modifying. It reaches a maximum of 11.6v but when I put it almost to the minimum it reaches a minimum 3.68v but when I lower it more the poteiometer jumps to 5.6v. Also when I turn it on I hear a spark and the lamp on my table dims for a few milliseconds, what is happening?

 

Like I said they are unstable sometimes, you need shorter wires, ideally a preset is better than a large potentiometer.

 

Like I said they are unstable sometimes, you need shorter wires, ideally a preset is better than a large potentiometer.

One more question, how can I measure the max amperage of this power supply? I only have a multimeter

 

And nicrom wire

 

Looking at the chip and Transformer type , I would say 2Amps maximum. The chip looks like a Viper22a.

 

thanks! the ic is 1a154

 

Hello,

@Dodgydave , You could be right about the amperage.
The page given in the first post shows a power supply of 2 A.

Bertus