Many already know that I have a weakness for all kinds of power supplies, here is a two-in-one review. This time there will be an overview of the radio designer, which allows you to assemble the basis for a laboratory power supply and a variant of its real implementation.
I warn you, there will be a lot of photos and text, so stock up on coffee :)

To begin with, I will explain a little what it is and why.
Almost all radio amateurs use such a thing as a laboratory power supply in their work. Whether it's complex with software control or very simple on the LM317, it still does almost the same thing, powering different loads in the process of working with them.
Laboratory power supplies are divided into three main types.
With impulse stabilization.
with linear stabilization
Hybrid.

The former incorporate a pulsed controlled power supply, or simply a pulsed power supply with a PWM buck converter. I have already reviewed several options for these power supplies. , .
Advantages - high power with small dimensions, excellent efficiency.
Disadvantages - RF ripple, the presence of capacitive capacitors at the output

The latter do not have any PWM converters on board, all adjustment is carried out in a linear way, where the excess energy is dissipated simply on the regulating element.
Pros - Virtually no ripple, no need for output capacitors (almost).
Cons - efficiency, weight, size.

The third ones are a combination of either the first type with the second, then the linear stabilizer is powered by a slave PWM buck converter (the voltage at the output of the PWM converter is always maintained at a level slightly higher than the output, the rest is regulated by a transistor operating in linear mode.
Either this is a linear power supply, but the transformer has several windings that switch as needed, thereby reducing losses on the regulating element.
This scheme has only one minus, the complexity, it is higher than the first two options.

Today we will talk about the second type of power supply, with a regulating element operating in linear mode. But consider this power supply using the example of a designer, it seems to me that this should be even more interesting. Indeed, in my opinion, this is a good start for a novice radio amateur, to assemble one of the main instruments for himself.
Well, or as they say, the right power supply should be heavy :)

This review is more aimed at beginners, experienced comrades are unlikely to find anything useful in it.

I ordered a constructor for review, which allows you to assemble the main part of the laboratory power supply.
The main characteristics are as follows (from the ones declared by the store):
Input voltage - 24 Volts AC
The output voltage is adjustable - 0-30 Volts DC.
Output current adjustable - 2mA - 3A
Output voltage ripple - 0.01%
The dimensions of the printed board are 80x80mm.

A little about the packaging.
The designer came in a regular plastic bag, wrapped in a soft material.
Inside, in an anti-static bag with a latch, were all the necessary components, including the circuit board.

Inside, everything was a mound, but nothing was damaged, the printed circuit board partially protected the radio components.

I will not list everything that is included in the kit, it's easier to do it later in the course of the review, I can only say that I had enough of everything, even something left.

A little about the printed circuit board.
The quality is excellent, the circuit is not included, but all the ratings on the board are indicated.
The board is double-sided, covered with a protective mask.

Board coating, tinning, and the very quality of the textolite is excellent.
I only managed to tear off a patch from the seal in one place, and then, after I tried to solder a non-native part (for some reason, it will be further).
In my opinion, the most for a novice radio amateur, it will be hard to spoil.

Before installation, I drew a diagram of this power supply.

The scheme is quite thoughtful, although not without flaws, but I will talk about them in the process.
Several main nodes are visible in the diagram, I separated them with a color.
Green - voltage regulation and stabilization unit
Red - current adjustment and stabilization unit
Violet - node indicating the transition to the current stabilization mode
Blue - reference voltage source.
Separately, there are:
1. Input diode bridge and filter capacitor
2. Power control unit on transistors VT1 and VT2.
3. Protection on the transistor VT3, turning off the output until the power of the operational amplifiers is normal
4. Fan power stabilizer, built on the 7824 chip.
5. R16, R19, C6, C7, VD3, VD4, VD5, unit for forming the negative pole of the power supply of operational amplifiers. Due to the presence of this node, the PSU will not work simply from direct current, it is the AC input from the transformer that is needed.
6. C9 output capacitor, VD9, output protection diode.

First, I will describe the advantages and disadvantages of the circuit design.
Pros -
I am glad that there is a stabilizer to power the fan, but the fan is needed for 24 volts.
I am very pleased with the presence of a negative polarity power supply, this greatly improves the operation of the PSU at currents and voltages close to zero.
In view of the presence of a source of negative polarity, protection was introduced into the circuit, until this voltage is present, the PSU output will be turned off.
The PSU contains a reference voltage source of 5.1 Volts, which not only allowed to correctly regulate the output voltage and current (with such a scheme, the voltage and current are regulated from zero to the maximum linearly, without “humps” and “dips” at extreme values), but also makes it possible to control external power supply, just change the control voltage.
The output capacitor is very small, which allows you to safely test the LEDs, there will be no inrush current until the output capacitor is discharged and the PSU enters current stabilization mode.
The output diode is necessary to protect the PSU from applying reverse polarity voltage to its output. True, the diode is too weak, it is better to replace it with another one.

Minuses.
The current sense shunt has too high a resistance, because of this, when operating with a load current of 3 Amperes, about 4.5 watts of heat is generated on it. The resistor is rated at 5 watts, but the heating is very large.
The input diode bridge is made up of 3 Amp diodes. For good, diodes should be at least 5 Amperes, since the current through the diodes in such a circuit is 1.4 of the output, respectively, in operation, the current through them can be 4.2 Amperes, and the diodes themselves are designed for 3 Amperes. The situation is only facilitated by the fact that the pairs of diodes in the bridge work alternately, but still this is not entirely correct.
The big disadvantage is that Chinese engineers, when selecting operational amplifiers, chose an op-amp with a maximum voltage of 36 Volts, but did not think that there was a negative voltage source in the circuit and the input voltage in this embodiment was limited to 31 Volts (36-5 = 31 ). With an input of 24 volts AC, the constant will be about 32-33 volts.
Those. The OU will operate in an extreme mode (36 is the maximum, standard 30).

I will talk about the pros and cons, as well as about the upgrade later, but now I will move on to the actual assembly.

First, let's lay out everything that is included in the kit. This will facilitate the assembly, and it will simply be more clearly visible what has already been installed and what is left.

I recommend starting the assembly with the lowest elements, because if you set high ones first, then it will be inconvenient to set low ones later.
It is also better to start by installing those components that are more of the same.
I'll start with resistors, and these will be 10 kΩ resistors.
The resistors are of high quality and have an accuracy of 1%.
A few words about resistors. Resistors are color coded. To many, this may seem inconvenient. In fact, this is better than alphanumeric marking, since the marking is visible in any position of the resistor.
Do not be afraid of color marking, at the initial stage you can use it, and over time it will be possible to determine it already without it.
To understand and conveniently work with such components, you just need to remember two things that will be useful to a novice radio amateur in life.
1. Ten basic marking colors
2. Ratings of the series, they are not very useful when working with precise resistors of the E48 and E96 series, but such resistors are much less common.
Any radio amateur with experience will list them simply from memory.
1, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.7, 3, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1.
All other denominations are the multiplication of these by 10, 100, etc. For example 22k, 360k, 39ohm.
What does this information give?
And she gives that if the resistor of the E24 series, then for example a combination of colors -
Blue + green + yellow in it is impossible.
Blue - 6
Green - 5
Yellow - x10000
those. according to calculations, it turns out 650k, but there is no such value in the E24 series, there is either 620 or 680, which means that either the color is recognized incorrectly, or the color is changed, or the resistor is not the E24 series, but the latter is rare.

Okay, enough theory, let's move on.
Before mounting, I shape the resistor leads, usually with tweezers, but some people use a small homemade device for this.
We are not in a hurry to throw away the cuttings of the conclusions, it happens that they can be useful for jumpers.

Having set the main amount, I reached single resistors.
It can be harder here, you will have to deal with the denominations more often.

I don’t solder the components right away, but I just bite and bend the conclusions, and I bite it first, and then bend it.
This is done very easily, the board is held in the left hand (if you are right-handed), at the same time the installed component is pressed.
There are side cutters in the right hand, we bite the conclusions (sometimes even several components at once), and immediately bend the conclusions with the side edge of the side cutters.
This is all done very quickly, after a while already on automatism.

So we got to the last small resistor, the value of the required and the one that remains is the same, already not bad :)

Having installed the resistors, we move on to diodes and zener diodes.
There are four small diodes here, these are the popular 4148, there are two 5.1 Volt zener diodes each, so it is very difficult to get confused.
They also form conclusions.

On the board, the cathode is indicated by a strip, as well as on diodes and zener diodes.

Although the board has a protective mask, I still recommend bending the leads so that they do not fall on adjacent tracks, in the photo the diode lead is bent away from the track.

The zener diodes on the board are also marked as markings on them - 5V1.

There are not very many ceramic capacitors in the circuit, but their marking can confuse a novice radio amateur. By the way, it also obeys the E24 series.
The first two digits are the value in picofarads.
The third digit is the number of zeros to be added to the face value
Those. for example 331 = 330pF
101 - 100pF
104 - 100000pF or 100nF or 0.1uF
224 - 220000pF or 220nF or 0.22uF

The main number of passive elements has been established.

After that, we proceed to the installation of operational amplifiers.
I would probably recommend buying sockets for them, but I soldered them as is.
On the board, as well as on the microcircuit itself, the first output is marked.
The rest of the pins are counted counterclockwise.
The photo shows a place for an operational amplifier and how it should be placed.

For microcircuits, I do not bend all the conclusions, but only a couple, usually these are the extreme conclusions diagonally.
Well, it's better to bite them so that they stick out about 1mm above the board.

Everything, now you can go to soldering.
I use the most common soldering iron with temperature control, but a regular soldering iron with a power of about 25-30 watts is quite sufficient.
Solder diameter 1mm with flux. I specifically do not indicate the brand of solder, since there is non-native solder on the coil (native coils weighing 1Kg), and few people will know its name.

As I wrote above, the board is of high quality, it is soldered very easily, I did not use any fluxes, only what is in the solder is enough, you just need to remember to shake off the excess flux from the tip sometimes.

Here I took a photo with an example of good soldering and not very good.
A good solder should look like a small droplet enveloping the lead.
But in the photo there are a couple of places where the solder is clearly not enough. This will happen on a double-sided board with metallization (where the solder also flows inside the hole), but this cannot be done on a single-sided board, over time such soldering can “fall off”.

The conclusions of the transistors must also be pre-molded, this must be done in such a way that the conclusion is not deformed near the base of the case (the elders will remember the legendary KT315, in which the conclusions liked to break off).
I shape powerful components a little differently. Molding is done so that the component is above the board, in which case less heat will transfer to the board and will not destroy it.

This is what the molded powerful resistors on the board look like.
All components were soldered only from the bottom, the solder that you see on the top of the board penetrated through the hole due to the capillary effect. It is advisable to solder in such a way that the solder penetrates a little to the top, this will increase the reliability of the soldering, and in the case of heavy components, their better stability.

If before that I molded the conclusions of the components with tweezers, then for the diodes I will already need small pliers with narrow jaws.
The conclusions are formed in much the same way as for resistors.

But there are differences when installing.
If for components with thin leads, installation first occurs, then biting, then for diodes the opposite is true. You simply won’t bend such a conclusion after biting, so first we bend the conclusion, then we bite off the excess.

The power unit is assembled using two transistors connected according to the Darlington circuit.
One of the transistors is mounted on a small heatsink, preferably through thermal paste.
There were four M3 screws in the kit, one goes here.

A couple of photos of an almost soldered board. I will not describe the installation of terminal blocks and other components, it is intuitive, and you can see it from the photo.
By the way, about the terminal blocks, there are terminal blocks on the board for connecting the input, output, fan power.

I have not washed the board yet, although I often do this at this stage.
This is due to the fact that there will be a small part of the refinement.

After the main assembly step, we are left with the following components.
Power transistor
Two variable resistors
Two board connectors
Two connectors with wires, by the way, the wires are very soft, but of a small cross section.
Three screws.

Initially, the manufacturer planned to place variable resistors on the board itself, but they are placed so inconveniently that I didn’t even solder them and showed them just for example.
They stand very close and it will be extremely inconvenient to regulate, although it is real.

But thank you for not forgetting to give wires with connectors in the kit, it's much more convenient.
In this form, the resistors can be placed on the front panel of the device, and the board can be installed in a convenient place.
Along the way, soldered a powerful transistor. This is an ordinary bipolar transistor, but with a maximum power dissipation of up to 100 watts (of course, when installed on a radiator).
There are three screws left, I didn’t understand where to even apply them, if at the corners of the board, then four are needed, if you attach a powerful transistor, then they are short, in general, a mystery.

You can power the board from any transformer with an output voltage of up to 22 Volts (24 is stated in the specifications, but I explained above why such a voltage cannot be used).
I decided to use a transformer for the Romantik amplifier that I had for a long time. Why for, and not from, but because he has not yet stood anywhere :)
This transformer has two output power windings of 21 Volts, two auxiliary windings of 16 Volts and a shielding winding.
The voltage is indicated for the input 220, but since we now have a standard of 230, the output voltages will also be slightly higher.
The calculated power of the transformer is about 100 watts.
I paralleled the output power windings to get more current. Of course, it was possible to use a rectification circuit with two diodes, but it won’t be better with it, so I left it as it is.

For those who do not know how to determine the power of a transformer, I made a short video.

First trial run. I installed a small radiator on the transistor, but even in this form there was quite a lot of heating, since the PSU is linear.
Adjustment of current and voltage occurs without problems, everything worked right away, so I can already fully recommend this designer.
The first photo is voltage stabilization, the second is current.

To begin with, I checked what the transformer outputs after rectification, as this determines the maximum output voltage.
I got about 25 volts, not a lot. The capacity of the filter capacitor is 3300uF, I would advise you to increase it, but even in this form the device is quite efficient.

Since for further verification it was already necessary to use a normal radiator, I proceeded to assemble the entire future structure, since the installation of the radiator depended on the intended design.
I decided to use the Igloo7200 radiator that I have. According to the manufacturer, such a radiator is capable of dissipating up to 90 watts of heat.

The device will use a Z2A case based on the idea of ​​Polish production, the price is about 3 dollars.

Initially, I wanted to move away from the case that bored my readers, in which I collect all sorts of electronic things.
To do this, I chose a slightly smaller case and bought a fan with a mesh for it, but I couldn’t put all the stuffing into it and a second case was purchased and, accordingly, a second fan.
In both cases, I bought Sunon fans, I really like the products of this company, and in both cases, 24 Volt fans were bought.

This is how I planned to install a radiator, a board and a transformer. There is even a little space left for expanding the filling.
There was no way to put the fan inside, so it was decided to place it outside.

We mark the mounting holes, cut the threads, screw them for fitting.

Since the selected case has an internal height of 80mm, and the board is also of this size, I fixed the heatsink so that the board is symmetrical with respect to the heatsink.

The conclusions of a powerful transistor also need to be molded a little so that they do not deform when the transistor is pressed against the radiator.

A small digression.
For some reason, the manufacturer conceived a place to install a rather small radiator, because of this, when installing a normal one, it turns out that the fan power regulator and the connector for connecting it interfere.
I had to solder them out, and seal the place where they were with tape so that there was no connection with the radiator, since there was voltage on it.

I cut off the extra tape on the reverse side, otherwise it turned out somehow completely sloppy, we will do it according to Feng Shui :)

This is how the printed circuit board looks like with the heatsink finally installed, the transistor is installed through thermal paste, and it is better to use good thermal paste, since the transistor dissipates power comparable to a powerful processor, i.e. about 90 watts.
At the same time, I immediately made a hole for installing the fan speed controller board, which in the end still had to be re-drilled :)

To set zero, I unscrewed both regulators to the extreme left position, disconnected the load and set the output to zero. Now the output voltage will be adjusted from zero.

A few tests follow.
I checked the accuracy of maintaining the output voltage.
Idling, voltage 10.00 Volts
1. Load current 1 Amp, voltage 10.00 Volts
2. Load current 2 Amperes, voltage 9.99 Volts
3. Load current 3 Amperes, voltage 9.98 Volts.
4. Load current 3.97 Amps, voltage 9.97 Volts.
The characteristics are very good, if desired, they can be improved a little more by changing the connection point of the voltage feedback resistors, but as for me, it’s enough.

I also checked the ripple level, the test took place at a current of 3 Amperes and an output voltage of 10 Volts

The ripple level was about 15mV, which is very good, though I thought that in fact the ripples shown in the screenshot were more likely to climb from the electronic load than from the PSU itself.

After that, I proceeded to assemble the device itself as a whole.
I started by installing a radiator with a power supply board.
To do this, I marked out the installation location of the fan and the power connector.
The hole was marked not quite round, with small "cuts" at the top and bottom, they are needed to increase the strength of the back panel after cutting the hole.
The biggest difficulty is usually the holes of complex shape, for example, under the power connector.

A large hole is cut from a large pile of small ones :)
Drill + drill with a diameter of 1mm sometimes work wonders.
Drill holes, lots of holes. It may seem that it is long and tedious. No, on the contrary, it is very fast, the complete drilling of the panel takes about 3 minutes.

After that, I usually put the drill a little more, for example 1.2-1.3mm and go through it like a cutter, it turns out such a cut:

After that, we take a small knife in our hands and clean the resulting holes, at the same time we cut the plastic a little if the hole turned out to be a little smaller. The plastic is quite soft, so it's comfortable to work with.

The last stage of preparation is drilling mounting holes, we can say that the main work on the back panel is over.

We install a heatsink with a board and a fan, try on the result, if necessary, “finish it with a file”.

Almost at the very beginning, I mentioned refinement.
I will work on it a little.
To begin with, I decided to replace the native diodes in the input diode bridge with Schottky diodes, I bought four pieces of 31DQ06 for this. and then I repeated the mistake of the board developers, buying by inertia diodes for the same current, but I had to have a larger one. But all the same, the heating of the diodes will be less, since the drop on Schottky diodes is less than on conventional ones.
Secondly, I decided to replace the shunt. I was not satisfied not only with the fact that it heats up like an iron, but also with the fact that about 1.5 Volts falls on it, which can be put into action (in the sense of a load). For this, I took two domestic 0.27 Ohm 1% resistors (this will also improve stability). Why the developers didn’t do this is not clear, the price of the solution is absolutely the same as in the version with a native 0.47 Ohm resistor.
Well, rather as an addition, I decided to replace the native filter capacitor 3300uF with a better and more capacious Capxon 10000uF ...

This is what the resulting design looks like with the replaced components and the fan thermal control board installed.
It turned out a little collective farm, and besides, I accidentally ripped off one patch on the board when installing powerful resistors. In general, it was possible to safely use less powerful resistors, for example, one 2-watt resistor, I just didn’t have this available.

A few components have also been added to the bottom.
3.9k resistor, parallel to the extreme contacts of the connector for connecting the current regulation resistor. It is needed to reduce the adjustment voltage, since the voltage on the shunt is now different.
A pair of 0.22uF capacitors, one in parallel with the output from the current control resistor, to reduce interference, the second is just at the output of the power supply, it is not really needed, I just accidentally took out a pair at once and decided to use both.

The entire power part is connected, a board with a diode bridge and a capacitor is installed on the transformer to power the voltage indicator.
By and large, this board is optional in the current version, but I didn’t raise my hand to power the indicator from its limiting 30 Volts and I decided to use an additional 16 Volt winding.

The following components were used to organize the front panel:
Load terminals
Pair of metal handles
Power switch
Red light filter, declared as a light filter for KM35 housings
To indicate current and voltage, I decided to use the board that I had left after writing one of the reviews. But I was not satisfied with small indicators and therefore larger numbers with a height of 14mm were bought, and a printed circuit board was made for them.

In general, this solution is temporary, but I even wanted to temporarily do it carefully.

Several stages of preparation of the front panel.
1. Draw the layout of the front panel in full size (I use the usual Sprint Layout). The advantage of using identical enclosures is that it is very easy to prepare a new panel, since the required dimensions are already known.
We apply the printout to the front panel and drill marking holes with a diameter of 1mm in the corners of the square / rectangular holes. With the same drill we drill the centers of the remaining holes.
2. According to the resulting holes, we mark the places of the cut. Change the tool to a thin disc cutter.
3. We cut straight lines, clearly in size in front, a little more in the back, so that the cut is as full as possible.
4. We break out the cut pieces of plastic. I usually don't throw them away as they might still come in handy.

Similarly to the preparation of the back panel, we process the resulting holes with a knife.
I recommend drilling large diameter holes, it does not "bite" the plastic.

We try on what we got, if necessary, modify it with a needle file.
I had to slightly widen the hole for the switch.

As I wrote above, for indication, I decided to use the board left over from one of the previous reviews. In general, this is a very bad solution, but more than suitable for a temporary option, I will explain why later.
We solder the indicators and connectors from the board, call the old indicators and the new ones.
I painted for myself the pinout of both indicators so as not to get confused.
In the native version, four-digit indicators were used, I used three-digit ones. because I no longer fit into the window. But since the fourth digit is needed only to display the letter A or U, their loss is not critical.
I placed the LED for indicating the current limiting mode between the indicators.

I prepare everything necessary, from the old board I solder a 50mΩ resistor, which will be used as before, as a current-measuring shunt.
This shunt is the problem. The fact is that in this version I will have a voltage drop at the output of 50mV for every 1 ampere of load current.
There are two ways to get rid of this problem, use two separate meters, for current and voltage, while powering the voltmeter from a separate power source.
The second way is to install a shunt in the positive pole of the PSU. Both options did not suit me as a temporary solution, so I decided to step on the throat of my perfectionism and make a simplified version, but far from the best.

For the construction, I used the mounting posts left over from the DC-DC converter board.
With them, I got a very convenient design, the indicator board is attached to the ampervoltmeter board, which in turn is attached to the power terminal board.
It turned out even better than I expected :)
I also placed a current-measuring shunt on the power terminal board.

The resulting front panel design.

And then I remembered that I forgot to install a more powerful protective diode. I had to solder it later. I used a diode left after replacing the diodes in the input bridge of the board.
Of course, for good it would be necessary to add a fuse, but this is no longer in this version.

But I decided to put the current and voltage adjustment resistors better than those suggested by the manufacturer.
The native ones are quite high-quality, and have a smooth run, but these are ordinary resistors, and as for me, the laboratory power supply should be able to more accurately adjust the output voltage and current.
Even when I was thinking of ordering a power supply board, I saw them in the store and ordered them for a review, especially since they had the same denomination.

In general, I usually use other resistors for such purposes, they combine two resistors inside themselves at once, for coarse and smooth adjustment, but recently I can’t find them on sale.
Maybe someone knows their imported counterparts?

The resistors are quite high quality, the angle of rotation is 3600 degrees, or in simple terms - 10 full turns, which provides a tuning of 3 Volts or 0.3 Amperes per 1 turn.
With such resistors, the adjustment accuracy is about 11 times more accurate than with conventional ones.

New resistors in comparison with relatives, the size is certainly impressive.
Along the way, I shortened the wires to the resistors a little, this should improve noise immunity.

I packed everything in the case, in principle, there was even a little space left, there is room to grow :)

I connected the shielding winding to the grounding conductor of the connector, the additional power board is located directly on the transformer terminals, this is of course not very neat, but I have not yet come up with another option.

Check after assembly. Everything started up almost the first time, I accidentally mixed up two digits on the indicator and for a long time could not understand what was wrong with the adjustment, after switching everything became as it should.

The last stage is gluing the light filter, installing handles and assembling the body.
The light filter has a thinning around the perimeter, the main part is recessed into the housing window, and the thinner part is glued with double-sided tape.
The handles were originally designed for a shaft diameter of 6.3mm (if I don’t confuse), the new resistors have a thinner shaft, I had to put a couple of layers of heat shrink on the shaft.
I decided not to design the front panel in any way yet, and there are two reasons for this:
1. Management is so intuitive that there is no special meaning in the inscriptions yet.
2. I plan to modify this power supply, so changes in the design of the front panel are possible.

A couple of photos of the resulting design.
Front view:

Back view.
Attentive readers must have noticed that the fan is positioned in such a way that it blows hot air out of the case, and does not force cold air between the radiator fins.
I decided to do this because the heatsink is slightly smaller than the case, and so that hot air does not get inside, I put the fan in reverse. This, of course, significantly reduces the efficiency of heat dissipation, but it allows you to slightly ventilate the space inside the PSU.
Additionally, I would recommend making a few holes from the bottom of the bottom half of the case, but this is more of an addition.

After all the alterations, I got a current slightly less than in the original version, and amounted to about 3.35 Amperes.

And so, I will try to paint the pros and cons of this board.
pros
Excellent workmanship.
Almost correct circuitry of the device.
A complete set of parts for assembling the power supply stabilizer board
Good for beginner radio amateurs.
In a minimal form, only a transformer and a radiator are additionally required, in a more advanced form, an ampervoltmeter is also required.
Fully functional after assembly, although with some nuances.
The absence of capacitive capacitors at the PSU output, it is safe when checking LEDs, etc.

Minuses
The type of operational amplifiers is incorrectly selected, because of this, the input voltage range should be limited to 22 Volts.
Not a very suitable current measurement resistor value. It works in its normal thermal mode, but it is better to replace it, since the heating is very large and can harm the surrounding components.
The input diode bridge is working at maximum, it is better to replace the diodes with more powerful ones

My opinion. During the assembly process, I got the impression that the circuit was developed by two different people, one applied the correct principle of adjustment, reference voltage source, negative voltage source, protection. The second one incorrectly selected a shunt, operational amplifiers and a diode bridge for this case.
I really liked the circuitry of the device, and in the refinement section, I first wanted to replace the operational amplifiers, I even bought microcircuits with a maximum operating voltage of 40 volts, but then I changed my mind about modifying it. but otherwise the solution is quite correct, the adjustment is smooth and linear. Of course there is heating, without it nowhere. In general, as for me, for a beginner radio amateur this is a very good and useful constructor.
Surely there will be people who will write that it’s easier to buy ready-made, but I think that it’s more interesting to assemble it yourself (probably this is the most important thing) and more useful. In addition, many quite calmly at home have both a transformer and a heatsink from an old processor, and some kind of box.

Already in the process of writing a review, I had an even stronger feeling that this review would be the beginning of a series of reviews dedicated to a linear power supply, there are thoughts for improvement -
1. Translation of the indication and control circuit into a digital version, possibly with a connection to a computer
2. Replacing operational amplifiers with high-voltage ones (I don’t know which ones yet)
3. After replacing the op amp, I want to make two automatically switching stages and expand the output voltage range.
4. Change the principle of current measurement in the display device so that there is no voltage drop under load.
5. Add the ability to turn off the output voltage with a button.

That's probably all. Maybe I'll remember something and add, but more I'm waiting for comments with questions.
Also, I plan to devote a few more reviews to designers for beginner radio amateurs, maybe someone will have suggestions about certain designers.

Not for the faint of heart

At first I didn’t want to show it, but then I decided to take a photo anyway.
On the left is the power supply that I used for many years before.
This is a simple linear PSU with an output of 1-1.2 Amperes at a voltage of up to 25 Volts.
So I wanted to replace it with something more powerful and correct.

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