Радиометр Луч: реставрация и обзор
Hello, friends! I know there are a lot of people on my channel, who like to watch about the restoration of devices, and today there will be a video for them. I got a Luch radiometer with a difficult fate. Judging by the stickers on the case, it worked as intended for a very long time and experienced all the hardships of life, and then it was sold from hand to hand several times… The radiometer had been on sale on Avito for over a year, but the price was inadequate for a long time, and no one wanted to take it, then someone bought it anyway, but during delivery it was damaged and returned back.
And I felt so sorry for the device that I bought it back – solely for the purpose of restoration. Because I understand that no one else will deal with it except me. Well, and the device that worked for many years and brought benefit to people, definitely deserves good treatment. As you can see, it looks pretty bad.
This serious dent Luch received during the last delivery, because of which it was returned to the seller. Not only the outer casing sagged, but also the chassis inside. And that's what upsets me the most. The paint is in so-so condition, lots of dirt, several stickers, somewhere the paint is peeling off. The power supply connector has been torn out. The microammeter needle is shifted from the zero position and is not adjustable with a corrector.
The range selector knob is not original, should be like this. The bottom of the casing is very peeling. I don't even know how to paint this. The cable is taped with electrical tape on the connector side.
The rubber handle is torn and also wrapped with electrical tape. There is deformation of the sensor screen. The inside of the console is also not very good. The aluminum chassis is severely deformed. As I already said, there is no mains connector with wires. One of the terminals for connecting the power cells is broken.
There is rust on the screws. The aluminum chassis has traces of oxidation from leaking batteries. And also oxides in the lower casing.
The elastic band for fastening the power cells is stretched. And even without opening the chassis, you can see, that instead of the standard triode P3V some later transistor is used. Well, as you may have guessed, there is nothing else in the kit – no other sensors, no box, no spare parts. On the whole, it’s scary to even imagine, how much this Luch has endured during his working life. They killed him as best they could.
But the good news is that the Luch works. And let's make sure of this. A lithium-ion battery can be used for power supply.
I think you are already well acquainted with the way for working with radiometers. First, turn the power knob to the left, then turn on the device in the “Battery” mode. You need to wait a little bit, and then you can adjust the supply voltage of the counters.
Now let's switch to working mode. Clicking sounds are heard, and when bringing the source Luch reacts to it correctly. This is very good, the radiometer is working properly, and it will be more fun for me to work on it. I also wanted to check the operation of the device from the mains. The connector is ripped out here, but we can connect to the terminals directly.
Before we do this, I checked the resistance of the windings of the transformer using a multimeter, and it turned out to be normal – there doesn't seem to be any break or short circuit here. There is also a capacitor MBGP in the power supply circuit at 0.25 μF, and it also lives up to its value.
Well, the resistor is also fine. There are no other parts, we can turn it on. But unfortunately, when trying to turn it on, the device shows no signs of life. I looked at the schematic diagram again and found that the power regulator should consist of two potentiometers, that is, there must be two variable resistors on one axis. The first one is for battery power mode, the second one is for power supply from the mains.
And in my Luch there is only one. And instead of the second potentiometer I found two cut wires in electrical tape. So the question of mains power supply we'll solve something later.
First, I'll clean the outside of the radiometer, and then I will gradually solve the problems. The results of the cleaning are as follows. The top panel is in good condition and requires only minimal touch-up painting. Using hammer enamel and a thin brush I will fix all the damage.
But the lower casing was damaged very badly. On the bottom, the paint is lost over a large area, there are a lot of scratches down to the metal on the side walls, there are also some scuffs and peeling coating. Initially, I planned to paint everything locally with a brush, but scratches cannot be removed this way.
I would really like to keep the original paint, but still I am inclined to completely repaint the casing. The interior is heavily damaged by oxidation, quite deep caverns are visible at the bottom. In areas of strong acid exposure the silver paint has dissolved. I'll putty the caverns, because it is very easy to do, and then I will paint the casing from the inside with a suitable enamel.
But first I need to straighten out the dent on the body. To do this, I dismantle the switch and the speaker, and I will try to bend the dent back. I'll try using a clamp and some wooden pieces like these. Well, it seems like everything worked out, at least it definitely got better. We still need to straighten the chassis as much as possible.
In principle, it is not necessary to straighten everything perfectly here, the main thing is that it is not as crooked as it is now. I have more or less corrected the obvious deformations of the chassis, although it is far from ideal. But to do better there was simply no way to do this without a complete disassembly, so I'll stop here. I also cleaned up some of the oxides and rust.
The next step is to paint the casing. First I'll fill in the necessary places and then apply enamel. I will paint the inside silver. Outside – hammer enamel. Here is a Sputnik radiometer sensor for comparison, which I painted earlier, and this result suits me more than well, everything looks very close to the original. While the enamel is drying, I decided to remove the measuring head and see what the problem is.
The seller said that the needle had shifted after that very side impact on the body of the radiometer. I'll try to adjust it, but as a last resort I have a spare microammeter. Anyway, I fiddled a bit with bending the pointer, and something worked out, although the idea itself is not very good.
However, we can still check the adequacy of the readings, if we connect another microammeter. And look, the pointers work quite synchronously, so the repair was quite successful. Yes, to be honest, the head needs to be replaced, but for my conditional measurements this option will also work.
It's time to get into mains power supply. I received dual potentiometers, and now from the two I need to assemble one with the required values. The first copy consists of two modules, 470 Ohm and 1.5 kOhm, we need the one on the bottom, 470 ohms. And the second one consists of 2 parts of 1 MOhm, and we need to take the top one, which is marked with the letter “A”, what does linear characteristic mean.
Luckily, swapping the right parts around is very easy. We bend the latches with a screwdriver. And we remove the potentiometer. We do the same with the second one. Now we insert one into the other, bend the latches, and everything is ready.
All that remains is to replace the old Luch potentiometer with a new one. And, of course, it is necessary to restore the missing parts. We take a special instrument connector, we solder wires to it, we install the connector into the case, we connect the wires to the terminals. And now we need to make a power cord, for this we will need a Soviet plug, the second part of the instrument connector and cable.
I'll do everything behind the scenes. Now the moment of truth, the first switch-on. I hope nothing goes boom. Power supply is adjustable. We turn on the working mode. Everything works! Everything works.
Well, I didn't doubt it, but it's still nice. Let's go back inside the console for a moment. I replaced the broken terminal, although it was not really needed. As for the non-standard transistor MP42B, which works here instead of the original P3V, then I decided not to change it.
First of all, it works properly, secondly, it has better characteristics, thirdly, I don’t have a P3V and I have no desire to buy one. Besides, both of these transistors are Soviet, germanium, so there is no point in getting into something where everything is already fine. I checked all the other parts, they fully correspond to their nominal values. I consider this to be the end of the work on the Luch console.
Now we move on to the sleeve. I straightened the sensor rim as much as possible, and painted it with silver paint. I didn’t film this process, there was nothing interesting there. All that remains is to remove the tape from the handle and the connector. The connector lacks a rubber cable damper, and it will have to be printed.
More likely, I will also use electrical tape to secure the cable, and I'll put a damper on top. But for now the exact actions are not clear to me, I'll figure it out as we go. The handle is quite badly deformed, I'll try to restore its shape, but if it doesn't work out, then as a last resort I have an option to print the rubber pad on a printer.
I had to trim the pad a little to get it to line up, but now it can be glued back in place. I also accidentally noticed, that the handle was missing a damper spring, so I installed it. I slowly took apart the connector, inside I saw terrible quality assembly, which will need to be redone. All connector parts had to be thoroughly washed. I painted the cap black, as it should be in the original. I printed the missing rubber damper on a printer.
Now we can put all the parts on the cable, and solder the wires to their terminals. Well, all that's left is to put it all together. It didn't turn out quite like the original, but certainly much better than it was. Well, that completes the restoration as a whole. There are still some little things I didn't capture on video.
The radiometer now looks, although not like new, but not like the old one anymore. Functionally everything is fine, I restored the mains power supply, well, and by the way, with a new potentiometer the power supply is regulated more smoothly. I removed all the tape from the parts of the sleeve, brought it back to normal. I repaired the head using a somewhat barbaric method, but I repeat once again that in my case it is acceptable, especially since I checked the adequacy of its readings. I also washed and cleaned everything inside.
Checked the parts for compliance with the nominal values. Now I can safely use Luch, I am happy with the restoration. Now let's do a quick overview of the Luch radiometer. It appeared in the late 50s of the last century and was produced for several years at the well-known to us “Radiopribor” plant. The purpose of the radiometer is a quantitative and qualitative definition of gamma and beta radiation and beta particle flux density.
Thanks to dual power supply, both from batteries and from the mains, Luch could be used both in the field and in laboratory conditions. The body of the radiometer is made of aluminum, the dimensions of the console are 222×140×112 mm, and the mass is 4 kg. It has moisture protection elements and is capable of operating in a wide temperature range from –20 to +50 degrees.
The device came with 4 different sensors, two of them are with mica counters SBT-7 and SBT-9, and two with metallic STS-5 and STS-6. Mica counters were used to work with soft beta radiation, while the STS meters were intended for recording hard beta and gamma radiation. All meters had a set of different screens to filter out both soft and hard beta. It should be noted that the radiometer was produced in two versions: Luch-A with 4 sensors, and just Luch with a special sensor to measure beta contamination of air, the so-called filter-ventilation alarm. And I have a console for exactly this kind of device, because it is simply called Luch without the letter A.
But they are completely interchangeable and have only minor differences in the circuitry. The top panel of the console contains the controls for the device. There is a switch on the left, with which the radiometer is turned on in mains or battery mode. Here you can also select the silent measurement mode or work with sound.
As we already know, for ease of work the Luch radiometer has a built-in speaker, which voices the pulses registered by the counter. In the lower left part of the body there is a connector for connecting the mains power supply. The device can operate in a wide range of voltages from 100 to 240 volts. And on the side of the top panel there is a 4-pin connector for connecting the sleeve. The sleeve is exactly the same as that of the Razvedchik radiometer.
It has a telescopic design to change the length of the rod, and also a hinge joint to install the meter at the desired angle. Some radio components are located inside the sleeve body, these are two TX-4B thyratrons, several resistors and capacitors. On the right side of the console is located subrange and power setting mode switch.
Luch has 4 working subranges: from 0 to 20 pulses/sec, up to 100, up to 500 and up to 1000 pulses/sec. The scale of the device is graduated accordingly, in pulses per second from 0 to 10. To determine the value, you need to multiply the scale readings by the set coefficient of the selected subrange. Below is the “Reset” button, which serves to reset the readings. And more lower is the power mode regulator. To set the correct voltage on the counter it is necessary to align the needle with a special mark on the scale at number 6.
After this, you can switch the device to the working subrange. Let's turn on the first subrange. Right now our needle is hovering around the 3 mark, which corresponds to 6 pulses per second.
We can increase the radiation power, and we will need to move to the ×10 subrange. We use the scale to determine the flow density approximately equal to thirty pulses/sec. But the impulses themselves don’t mean anything, because they depend on the installed meter, however, the manual provides conversion factors to dose rate and beta flux density. I already said, that my Luch has only one sensor with a SBT-7 counter, however, the sensors from the Razvedchik radiometer, which I have, are also suitable for the device. Even more than that, the sensor with the STS-6 counter is absolutely identical, so we can connect this sensor to Luch. It has a removable screen, which allows us to differentiate gamma radiation from a mixed beta/gamma flux.
It is interesting that if we measure the supply voltage of the meter when the power is set correctly, then instead of the 400 volts we are used to, we will see 380. This is not a defect of this particular specimen, but the fact is that that the SBT-7 meter has an operating voltage of 380 volts, that is why Luch is tuned to exactly this value. Let's open the device case again and let's turn our attention to the chassis.
The thought immediately arises that we have seen this somewhere before. This board is very typical, with capacitors and resistors placed on it, and next to it is a selenium rectifier and a gas voltage stabilizer. And indeed, if you compare the composition of the components with Sputnik or Razvedchik radiometers, it turns out that the circuit of these devices is practically the same only with an amendment for the additional mains power supply at Luch and a slight difference in the subranges.
Personally, I really like this circuitry – it is simple and extremely easy to maintain. Any radiometer from this line of devices very easy to diagnose and repair. Luch radiometer was extremely successful in terms of functionality and reliability. This copy that I have in my hands was produced in 1962 and worked for more than 50 years! It was used until at least 2015. The device was repaired several times, some parts were replaced, but the radiometer had no intention of retiring.
I am glad that this Luch came to me in exactly this state, in which you saw it at the beginning of the video. Even though my restoration is not perfect, but I was pleased to bring the radiometer into a decent condition, which it absolutely deserved. Thanks everyone for watching, see you in new videos!
2025-01-02 23:46
