Hello, you will learn about the serviceability of the shim. Let’s look at its main types and features of use. There will be many more detailed examples and descriptions. In order to better understand what PWM serviceability and PWM repair are, I strongly recommend reading everything from the category Diagnostics, maintenance and repair of electronic and radio equipment
Pulse-width converters are a structural part of switching power supplies for electronic devices. Let's look at how to check a PWM controller using a multimeter, using the example of a computer motherboard.
Finding faulty PWM block
In an ultra-fast and simple method, a faulty PWM controller block can be determined indirectly by checking the corresponding throttles with a homemade device.
Let's remember a little theory. Around each transformer, or inductor, with a significant number of turns, after turning on the power to the circuit, there is a magnetic field, and it is greater, the more turns the winding of the transformer, or inductor, has. If we bring another inductor loaded with an LED to the winding of a transformer or inductor connected to the device network, then the magnetic field of the inductor or transformer will penetrate the turns of our inductor, and a voltage will appear at its terminals, which can be used, in our case, for indication of the operability of circuits that contain chokes or pulse transformers. Of course, you need to bring the probe as close as possible to the part being tested.
3844b
Welcome to the store Payment: We accept Alipay, Payment must be completed within 3 days of order If you can't checkout immediately after auction, please wait for a few minutes and retry Payments must be completed within 3 days. Delivery: We guarantee delivery within 48 hours after payment confirmation except holidays. EMS express delivery usually takes business days depending on the country of delivery. We are not responsible for any accidents, delays or other issue that are the responsibility of the shipping service.
Search data for your request:
Checking the PWM controller on the computer motherboard
If, when you turn on the power to the board, the protection is triggered, then you need to check the resistance of the stabilizer arms with a multimeter.
A radio components tester can also be used for these purposes. The website https://intellect.icu talks about this. If one of them shows a short circuit, that is, the measured resistance is less than 1 Ohm, then one of the key field-effect transistors is broken.
Determination of a broken transistor if the stabilizer is single-phase is made based on the fact that the faulty device, when tested with a multimeter, shows a short circuit.
If the stabilizer circuit is multiphase (this is how the processor is powered), then parallel connection of transistors is used.
Then, you can find the damaged element in two ways:
- desolder the transistor and check the resistance between its terminals with a multimeter for breakdown;
- Without soldering the transistors, measure and compare the resistance between the gate and source in each phase of the converter. The damaged area is identified by a lower resistance value.
The second method does not work in all cases.
If the broken element could not be determined, you will still have to unsolder the transistor.
Next, the damaged transistor is replaced, and all radio elements that were soldered off during the diagnostic process are replaced. After this, you can try to start the board.
The first startup after repair is best done by removing the processor and setting the appropriate jumpers. If the first run was successful, you can carry out a load test, monitoring the temperature of the mosfets.
Malfunctions of the PWM controller can manifest themselves in the same way as a breakdown of the mosfets, that is, the power supply goes into protection. At the same time, checking the transistors themselves for breakdown does not give any results.
In addition, the consequence of a malfunction of the PWM controller may be the absence of output voltage or its discrepancy with the nominal value. To check the PWM controller, you should first study its datasheet. The presence of high-frequency voltage in pulse mode, in the absence of an oscilloscope, can be determined using a quartz tester on a microcontroller.
Scientists have discovered a “double” of the Earth
An exoplanet located relatively close to the solar system and considered similar to Earth does not have any signs of life, astronomers have found. We are talking about the planet LHS b. It is 1.3 times larger than Earth and orbits a dim star at a fairly close distance. A full revolution around the star takes 11 days. Scientists believed that the space object must receive enough heat to have liquid water on the surface, Nature reports.
But recent evidence suggests that the planet is completely devoid of an atmosphere. Observations with the Spitzer telescope revealed no carbon dioxide or nitrogen. According to scientists, if a gas shell exists, it is as thin as on Mars, and therefore cannot protect the surface from cosmic radiation. The study authors concluded that LHS b is most likely a barren basalt desert where the hardiest microorganisms cannot exist. It was previously reported that the Milky Way may contain about ten billion Earth-like planets.
Application for organizing a broadcast. Contact the Company. Procurement and tenders. Advertising department: reklama mir Planning department: vmeste intmir. Website: Alexey Tikhonov. More details in the story: Space Astronomers explained the bright flash on Jupiter In the center of the Milky Way, traces of an explosion were found 60 years ago, the first photographs of the far side of the Moon were taken. Online publication. Editor-in-Chief: Batyrshin R.
The certificate was issued by the Federal Service for Supervision of Communications, Information Technologies and Mass Communications. All rights to any materials published on the site are protected in accordance with Russian and international laws on copyright and related rights.
Online broadcasting of a broadcast stream on the Internet without approval is strictly prohibited. Broadcasting is possible only when using the player and online broadcasting system of the MTRK Mir Closed Joint Stock Company. For correspondence: , Moscow, Krasnobogatyrskaya street, no.
Symptoms of a PWM unit malfunction and their elimination
Stopping immediately after starting
The pulse modulator starts but immediately stops. Possible reasons: open feedback circuit; the power supply is overloaded; The filter capacitors at the output are faulty.
Finding the problem: inspecting the board, looking for visible external damage; Using a multimeter to measure the supply voltage of the microcircuit, the voltage on the switches (at the gates and at the output), and at the output capacitors. In ohmmeter mode, use a multimeter to measure the load of the stabilizer and compare it with the typical value for similar circuits.
Pulse modulator does not start
Possible reasons: presence of a prohibiting signal at the corresponding input. Information should be found in the datasheet of the corresponding microcircuit. The malfunction may be in the power supply circuit of the PWM controller, or there may be internal damage in the microcircuit itself.
Steps to determine the malfunction: external inspection of the board, visual search for mechanical and electrical damage. To check, use a multimeter to measure the voltages on the pins of the microcircuit and check their compliance with the data in the datasheet; if necessary, you need to replace the PWM controller.
Voltage problems
The output voltage differs significantly from the nominal value. This can happen for the following reasons: a break or change in resistance in the feedback circuit; a fault inside the controller.
Troubleshooting: visual inspection of the circuit; checking the levels of control and output voltages and checking their values with the datasheet. If the input parameters are normal, but the output does not correspond to the nominal value, replace the PWM controller.
Disabling the power supply by protection
When the pulse-width modulator starts, the power supply is turned off by protection. When checking the key transistors, a short circuit is not detected. Such symptoms may indicate a malfunction of the PWM controller or key driver.
In this case, it is necessary to measure the resistance between the gate and source of the switches in each phase. A low resistance value may indicate a driver malfunction. If necessary, drivers are replaced.
That's all! Now you know everything about the serviceability of the shim. Remember that this will now be easier to use in practice. I hope that now you understand what shim serviceability, shim repair is and why all this is needed, and if you don’t understand, or if you have any comments, then don’t hesitate to write or ask in the comments, I will be happy to answer. In order to gain a deeper understanding, I strongly recommend that you study all the information from the category Diagnostics, maintenance and repair of electronic and radio equipment
IBEP 220/24V PNS is faulty (PWM UC3844)
There is an uninterruptible power supply (UPS) from.
The stabilizing voltage converter (VNS) is faulty: there is no power at the output.
IBEP is necessary for the uninterrupted operation of the self-propelled control system of the gas distribution system.
The batteries are swollen - perhaps this is the reason for the malfunction of the second PNS within one year.
Can you share good sources of information on repairing switching power supplies (preferably with a UC3844 PWM)?
After reading this post, can you tell me what else to check?
IBEP includes 3 PNS, 2 of which stopped working. PNS with PWM switch uc3844.
The first PNS was repaired
:
— the faulty starting capacitor (47uF/35V) and the PWM power capacitor (220uF/25V) were replaced. The two leftmost are in the picture below.
- a resistor (6.8k) was soldered into place, which self-sawed out due to overheating, but itself remained alive. It's not pretty, but let it be
I haven’t hooked up the load yet, my hands can’t reach it, but the output is 27V at idle. There is something humming during operation, but I think this is normal, but I’m not sure.
This is what a working control board of the first PNS
:
What was done first:
— the faulty starting capacitor (47uF/35V) was also replaced.
- the swollen capacitors (470 µF/25V) were replaced, the power supply for the second half of the circuit (PNS diagnostic logic?) - which are green ones.
— the 6.8 kOhm resistor is alive, although it looks overheated.
But the output is still nothing. Only the LED will blink (the PNS is working properly) and the switches will click, and there will be silence.
This is what the control board of the second PNS looks like (highlighted PWM and all its wiring):
I couldn’t find the diagram online, so I had to create it myself:
I wrote above the ShIMka that I intended it to be on legs when connected to the PNS network.
I immediately identified problem areas and points at the output, from where I measured the output signal from the PWM with an oscilloscope (+ measured a saw with 4 legs):
The saw oscilloscope readings at the PWM input and after the resistor at the output (Out) of the PWM are as follows:
The "hot" board looks like this:
The input/output shimka is connected to the pin plug at the bottom left
(from the drawn diagram:
11,12 - two leftmost pins (-280VDC about that),
13,14 - two rightmost pins (+280VDC about that),
the middle two pins supply voltage to the control board to the comparator P1401CA3
(on a working “control” board this is lm393p).
The “hot” board is OK
, since the repaired “control” board (from the First PNS) works with two “hot” boards, and the faulty one (from the second PNS) does not work with either one.
What else has been done:
- the key transistor was unsoldered and checked with a multimeter and according to the ESR meter it was identical to the transistor from the store.
— all capacitors were replaced and tested using an ESR meter, except for the small 10uF/50V (4 pieces) on the right side of the board.
If you do not insert the second plug into the “hot” board (which is on top of the picture of the control board), then the right side of the “control” board stops seeing the 3 volts coming from the input of the “hot” board and this logic gives a signal that the PNS is working, i.e. e. The green LED lights up. But thus no power appears at the output. This is understandable. this part of the “control” board is responsible for diagnosing the PNS.
The PNS itself looks like this with the “control” board removed.
I hope I wrote everything clearly. The repair took a long time, but this is not critical; in my free time I tinker with it and compare it with the working board.
I have little experience in repairing switching power supplies, and if I have, then basically everything was solved by replacing capacitors.
Thank you for your attention.
After a long fuck with IBEP, without regret I replaced it with UEPS-2k.
And I wish you the best, because IMHO it is impossible to use this unreliable junk as a power source for critical circuits and devices.
And, yes, if the shim/field switch dies, be sure to check the C7-R12/D2 chain.
Well, here's a C9 Conder and a field gun (+ a field gun from the store).
Shim is alive, and so is the field worker. It would be better if they died
We have been using UEPS at other facilities for a long time. This GDS is still in use and is still alive.
I also measured C7 and R12, but didn’t take a photo. If you try to stupidly replace it.
And about D2. Well, in general, I’m throwing off all the KD258B diodes, except for D3 (Shimka works, so there’s no point in checking it.).
Exoplanet LHS 3844b is unsuitable for terrestrial life - astronomers
3844b
After more than hours of observations using the Spitzer telescope, astronomers have concluded that the relatively nearby exoplanet LHS b, which orbits an M-class red dwarf, has no atmosphere. The planet was discovered last September by the new orbital telescope TESS. It is 48.6 light years away and has a radius 1.3 times that of Earth. A year on it lasts only 11 Earth hours, since its star is only 0, astronomical units distance from the Earth to the Sun, that is, only km.
Let's summarize the repair
By the current standards of the crisis and rising prices, someone, a resident of large cities, who has a high salary by Russian standards, can say that God knows what amount was saved, more of their time was spent. But if we return to the fact that there is now another crisis in the yard, saving this amount for most people who know how to hold a soldering iron in their hands, carry out diagnostics of devices and know how to count money, would hardly be superfluous, even if for assembling their own personal system unit. And if so, then people who have experience and practical knowledge in the field of electronics already have an advantage compared to people who do not have this knowledge and, accordingly, do not have this opportunity. Happy repairs to everyone, author of the article AKV.
Exoplanet LHS 3844b is unsuitable for terrestrial life - astronomers
Registration Forgot your password. When ordering, keep in mind that integrated circuits can have different types of housing, see the picture and parameters. Only the main purpose and characteristics parameters are published on our website. For additional questions, please contact us via email. A complete description and information on how to check UCB B smd, what to replace it with, the connection diagram, domestic analogue, Datasheets and other technical data can be found in the PDF files of our DataSheet section, in reference books, or on Google search engine sites , Yandex. Soldering and connecting all electronic components must be done by specialists. For example, by adding the tag “repair”, this product will appear in search results for that word.
NASA astronomers have found an exoplanet the size of Earth
Popular mechanics. Russia may stop producing craft beer. RT reports this with reference to Rosstandart. Another track, according to the minister, in the Cyprus settlement scenario is a complete freeze of the conflict, a complete cessation of interaction with the aggressor, the principle “a bad peace is better than a good war,” ed. Japanese Prime Minister Shinzo Abe said that his country believes that its sovereignty extends to the islands located in the southern part of the Kuril Islands, and Tokyo's position on this matter remains unchanged.
Scope of application
Almost all modern electronics are powered from blocks of this type, as an example:
- various types of chargers;
Chargers and external power supplies - external power supplies;
- electronic ballast for lighting fixtures;
- Power supply for monitors, TVs and other electronic equipment.
Monitor Switching Power Module
smd 3844b ic wholesale new and
Scientists from Harvard University believe that the list of potentially habitable planets in the Milky Way can be significantly reduced. Previously unexplored factors influencing the likelihood of the emergence of an atmosphere as a necessary condition for the origin of life are reported in the journal Nature. In this case, the total number of exoplanets in the Milky Way can reach 10 billion. LHS b revolves around its sun in a short hour-long orbit, with one side of the planet always facing the star, and the other always in the shadow. If the planet had an atmosphere, then some of the heat from the illuminated side would certainly be transferred to the dark side, the researchers say. The data obtained, according to experts, indicate the absence of an atmosphere at LHS b and suggest that the surface of the planet consists of dense rock, most likely basalt, and is a lifeless rock desert. Online publication rt. Editor-in-chief: Simonyan M. Editorial office address: Moscow, Borovaya street, 3k1.
The search is narrowing: exoplanets near dwarf stars turned out to be unsuitable for life
American astrophysicists have proven that the exoplanet LHS b has no atmosphere. If there was one, then the transfer of heat by the atmosphere would lead to more even daily temperature fluctuations. When scientists search for life on distant exoplanets, they favor rocky planets the size of Earth. Most so-called super-Earths orbit red dwarfs, the most common stars in the Milky Way. Their mass, as a rule, does not exceed a third of the Sun. And the luminosity can be ten thousand times less than that of the Sun. However, despite their dimness and small size, red dwarfs are many times more active than our star.
