Can you check on R4 which is 4k7 ohm on schematic but it seam is not the value install on your attach picture.

 

Hallo.
I have assembled and soldered everything and the result is Vout maxim= 27,6. Checked values and positions...one million times and the same Vout. suggestions?

 

Hallo.
I have assembled and soldered everything and the result is Vout maxim= 27,6. Checked values and positions...one million times and the same Vout. suggestions?

Are you still using the 16 volt transformer? That would explain the lower max output voltage. And the voltage divider of R12 and R11 is what delivers the feedback voltage to U2, the voltage control amplifier. Have you done the adjustment of RV1, which is supposed to null the offset on U2? and diode D9 is supposed to pull down the voltage setting when there is an overcurrent, so you should check to see that the output of U3 is still high.That will prevent D9 from conducting and limiting the output voltage. Then check the collector voltage of Q4 to see if the supply is even high enough.

 

I´m not using the 16 volt transformer. I have a 24 one. C1, (3300uF) gives 33 volt, so in the beginning I thought everything went right
When I did the adjustment of RV1was always 0,0 volts, despite I turned several rounds.
Anyway I´ll check all that you say me about D9, U3 and Q4 and I´ll write here to see what happends

 

OK, those test results show what the problem is not. So now the range of voltages at pins 2 and 3 of U2 as P1 is adjusted will tell us quite a bit. I am guessing that the problem is in the R11 and R12 area, or perhaps that C6 has some leakage.

 

Yeah, MisterBill2,
although I'm a little busy right now, I want to determine the cause of this problem. In addition to solving this, my intention is to get the correct voltages at various PCB points, like any technical service manual and edit it in the scheme we have.
Then I want to upload it, so that other users can get help and thus, and with all that information is much simpler, that you can assemble and launch this KIT with fewer problems than I for example have had without information.
But first, of course, I need the circuit to work completely...

 

Yeah, MisterBill2,
although I'm a little busy right now, I want to determine the cause of this problem. In addition to solving this, my intention is to get the correct voltages at various PCB points, like any technical service manual and edit it in the scheme we have.
Then I want to upload it, so that other users can get help and thus, and with all that information is much simpler, that you can assemble and launch this KIT with fewer problems than I for example have had without information.
But first, of course, I need the circuit to work completely...

That is a great idea and it should benefit a whole lot of folks as time passes, because power supplies are a basic part of many systems and projects. Documenting projects that have no instructions or explanations is a great idea. It might even convince the management of this site to add a section of "project documents" as another area. Or it might be called "how it works, or doesn't work", that would be very useful in this instance.

 

Well, here we are.
I have the same opinion, MisterBill2.
The power supply along with the soldering iron and a multimeter are the basic kit for any project.
"how it works, or doesn't work"; seems like a great idea to me, because sometimes you no longer know what to do when nothing works and there are people who already have that experience.

At the moment I have edited the original scheme of the kit.
I have written the values of the components in another color (blue), so you don't have to be looking at the part list separately, because at least for me it's very cumbersome and I like to have everything in the same scheme, at sight.
In order to make the annotations easier if you want to print and make everything look good, it is in DIN A3 size file.
As I haven't been able to continue with the circuit yet, I just added the 33 volt test point on the capacitor after the
filter (green).
I have uploaded it here in PDF format and I have edited it in the free soft Ikscape
I need you to tell me what you think. Does it look good? Is there a mistake somewhere?

 

Well, here we are.
I have the same opinion, MisterBill2.
The power supply along with the soldering iron and a multimeter are the basic kit for any project.
"how it works, or doesn't work"; seems like a great idea to me, because sometimes you no longer know what to do when nothing works and there are people who already have that experience.

At the moment I have edited the original scheme of the kit.
I have written the values of the components in another color (blue), so you don't have to be looking at the part list separately, because at least for me it's very cumbersome and I like to have everything in the same scheme, at sight.
In order to make the annotations easier if you want to print and make everything look good, it is in DIN A3 size file.
As I haven't been able to continue with the circuit yet, I just added the 33 volt test point on the capacitor after the
filter (green).
I have uploaded it here in PDF format and I have edited it in the free soft Ikscape
I need you to tell me what you think. Does it look good? Is there a mistake somewhere?

The drawing looks GOOD! And if it were in Autocad the different colors could be on different layers so that they could be switched on and off. In addition the spacing makes it easier to follow the circuit, which is handy when calibrating or analyzing the function. I don't see any mistakes but I also don't have the original in hand to check against. But I see no obvious goofs and nothing looks unreasonable.

 

The drawing looks GOOD! And if it were in Autocad the different colors could be on different layers so that they could be switched on and off. In addition the spacing makes it easier to follow the circuit, which is handy when calibrating or analyzing the function. I don't see any mistakes but I also don't have the original in hand to check against. But I see no obvious goofs and nothing looks unreasonable.

No problem with layers!! The soft I have used is Inkscape. Despite It is not a CAD or EDA/ECAD software, has the option to switch on /off the layer, and in fact I made the typicalls "image", "value", and "measurements". I had to use this one because the only format I found the original scheme was .jpeg and I think that was the most reasonable way to edit it..and of course is free and legal
Of course, I want to upload that file when I finish to complete it incluiding the test points we talked about

I would also like to add the typical faults when mounting the KIT for the first time, because the components come just right and buying them separately is sometimes more expensive than buying another new kit and when we connect the 24VAC transformer, if everything is not correct, it is easy to damage some component . . . and again to wait for a long time

 

No problem with layers!! The soft I have used is Inkscape. Despite It is not a CAD or EDA/ECAD software, has the option to switch on /off the layer, and in fact I made the typicalls "image", "value", and "measurements". I had to use this one because the only format I found the original scheme was .jpeg and I think that was the most reasonable way to edit it..and of course is free and legal
Of course, I want to upload that file when I finish to complete it incluiding the test points we talked about

I would also like to add the typical faults when mounting the KIT for the first time, because the components come just right and buying them separately is sometimes more expensive than buying another new kit and when we connect the 24VAC transformer, if everything is not correct, it is easy to damage some component . . . and again to wait for a long time

You can put a small pilot light bulb in series with the transformer connection to limit the current when you first switch it on. That is a handy trick I picked up a long time ago. And the light will give some hint about the amount of current, which is also useful.

 

Hey! That is a great trick! This week I received (at least) my toroid-transformer (I tested with other no-toroid one from other powet supply), and it is time to check the capacitor and resistances you told me.
What value is the suitable for the pilot light bulb?

 

Here is a simulation "save file" that I have put together for learning purposes.
Use this website www.falstad.com/circuit/circuitjs.html
and open my attach file to see for yourself.

 

Here is a simulation "save file" that I have put together for learning purposes.
Use this website www.falstad.com/circuit/circuitjs.html
and open my attach file to see for yourself.

This simulation website that you have published is really curious, and very effective, allows you to edit values and know the measures

 

OK, those test results show what the problem is not. So now the range of voltages at pins 2 and 3 of U2 as P1 is adjusted will tell us quite a bit. I am guessing that the problem is in the R11 and R12 area, or perhaps that C6 has some leakage.

R11, R12 and C6 measures are ok...good, c6 gives 103pF (I've done it with a T7-H, the typical Chinese meter I think measures well)
I have measured the resistances too, with a "normal" multimeter and also with the T7 and they are fine.There is a component or components despite measuring in theory fine are not working properly under load.

 

I update the information;
I recalibrated the multimeter. Now Vout gives 28,9 volts maximum and the power supply regulates well without load (with this I satisfied for the moment), but R1 (2K2/1W) gets very hot in just a few seconds and I have to disconnect immediately. I measured at the terminals of R1, which is parallel to C1 and are nothing less than 38 volts.
I continue to use the same 24AC transformer as before, and sometimes I don't know what' happends.

On the other hand and being positive, I have passed the electronic schema to a better format, since I'm using Kicad (I'm learning it while editing the schema).
It's great ECAD software!. . . and of course it's free, an excellent tool for students.
I'm documenting the project completely and when I finish it I'll upload it here as we've already commented.
Here I upload a sample of the pdf generated by the program and a screenshot of it

 

https://passive-components.eu/resistors-pulse-load-power-and-voltage-derating/

 

I can understand why the resistor R1,2200 ohms gets hot, and the reason for having such a low value directly across the supply input is not clear to me. It is not serving any really useful purpose. But the first check I would suggest is to verify the value of the resistor, in case it is mis-marked. If it is correct, the current through it should be about 15 milliamps =0.015A, (I=V/R=30/2200). So my first guess is that the resistor is actually 220 ohms. THAT would explain it getting hot.

 

useful purpose

it's common practice to avoid regulating "lack of load" situation in (otherwise) high power supplies -- it's easier to introduce min. load than go nuts designing a capability to regulate "Zero-draw"

 

it's common practice to avoid regulating "lack of load" situation in (otherwise) high power supplies -- it's easier to introduce min. load than go nuts designing a capability to regulate "Zero-draw"

A resistor loading the INPUT to a regulator is not preventing a lack of load condition. And certainly a resistor connected directly across the rectifier output is what is being discussed. Look at the circuit, R1 is what we are discussing.