I assume that the viewer has only a basic knowledge of electronics. Secrets of smps repair and troubleshooting switch mode. The output voltage rating of a power supply operating in the constant current mode analogous to the output current rating of a supply operating in the constant voltage mode. Most power supplies also have a voltage selector switch that lets it work with 110v or 220v power sources. This manual was originated from switching power supply user manual. A dummy load can be made from a couple lamps that you can buy at any auto parts store and an extension cable from radio shack. Jan 17, 2012 so far i found a blown power transistor 2n3771 on the back. Using a laptop or computer power supply repair can be extremely difficult especially for novice experts. As switching supplies become ubiquitous in electronic devices today. Here is what you get from the switch mode power supplies repair guide. Jun 02, 2017 similarly, components in the supply can operate at about 100 v in one state and at millivolts at another.
This manual includes basic information for switching power supply, general. A switchedmode power supply switching mode power supply, switchmode power supply, switched power supply, smps, or switcher is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. This reference manual contains useful background information on switching power. That one was easy because it unplugged for testing. Power supply failures can be a nightmare for a variety of reasons. Step 3 repairing samsung la40r81bd 40in lcd tv power supply clicking relay symptom inspect all electrolytic capacitors on the power supply board and replace any that are bulging or leaking.
Then use the thermal camera to observe where the board is heating up. The circuit that controls the switching transistor gets feedback from the power supply outputs, increasing. The repair of switch mode power supplies smps is economically a. A switching regulator does the regulation in the smps.
Im wondering if there is a way to run the ftmp mark v off of the mfj ps. The designs were complicated and some technicians found it quite hard to fully understand how the switch mode power supplies work. Chances are that if you used any computer for more than a few years without swapping out its power. The panasonic vcr power supply schematic is available in both pdf and gif format. Sep 16, 2018 the manual is perfect as a reference guide for computer power supply repair.
Notes on the troubleshooting and repair of small switchmode. Supply dead, fuse not blown bad startup circuit open startup. And a large part of that detail lies in the practical domain, largely because of the typically small number of microseconds of switching periods involved, and the even smaller tens of nanoseconds of switch transition times all these, in effect accentuating various secondorder effects, that eventually end up playing prime havoc with normal. You realize, this smps power source restoration manual is a important guide i use again and again. The voltage on the capacitor controls the time the series element is turned. Users should check whether there is breakdown, open circuit or damage on rectifier diode, hv filtering electrolytic capacitor, and inversion power. A typical pc power supply provides four dc out put voltages.
Current limit the power supply to a few amperes and apply power across the shorted terminals. When switch 1 mosfet 1 is on and switch 2 is off, the energy is transferred to the load rl through transformer, c2, and d1. How to repair a computer power supply or other switching. May 12, 2018 he said that if i cant get it working to let him have one of the repair gurus in his radio club look at it and see what they can do. Switch mode power supplies smps are now standard for the majority of our home appliances. When a switching regulator power supply fails, all three outputs will usually drop to zero volts. Whether you are an experienced power supply designer, designing your first switching power supply or responsible for a make or buy decision for power supplies, the variety of information in the switch. How to repair a switchmodepowersupply smps in this post we try to diagnose a burnt smps circuit and try to troubleshoot and repair the circuit. The continuous switching of the capacitor maintains the voltage at the required level.
Pdf this publication is a very good resource for someone beginning a career or entering education in the poert supply design field. Nov 01, 2007 very often when i attempt to repair electronic devices, either mine or from friends, i find out the problem is with the power supply which these days is most often a switched mode power supply smps. First the ac voltage will enter to a full wave rectifier bridge. Feb 06, 2011 switched mode power supply repair guide. The power supply fault could be an open start up resistor only or could be even more than ten components burnt due to heavy lightning strike. A series switching element turns the current supply to a smoothing capacitor on and off. Secrets of smps repair and troubleshooting switch mode power supply smps repair sometimes can be easy and sometimes are quite difficult to solve the problem. Repair vintage dc power supply, sorensen dcrb series 2700watt 6004. This article is written as per the request made by mr. Open shell of the power supply to check whether the power fuse has been blown. Power supply repair switch mode power supplies repair. For example, one common smps measurement is to determine switching loss and average power loss across the switching device.
In this article, im going to explain to you the power supply problems that caused by defective components at secondary side. Lcd and crt monitor power supplies, lcd tvs, dvd players, and many other electronic devices that contain a switch mode. Anatomy of switching power supplies hardware secrets. These volt ages are available through four different types of con nectors figure 1. Jul 09, 2018 old dental micro motor power supply problem. Constant current power supply a regulated power supply that acts to maintain its output current constant in spite of changes in load, line, temperature, etc. The repair of switch mode power supplies smps is economically a good investment for electronics repair shops and for hobbyists.
Aug 25, 2019 a bridge rectifier can be normally seen at the beginning of any smps circuit and is introduced primarily for rectifying the mains ac to a full wave dc, which is further filtered using a filter capacitor and applied to the mosfetinductor stage for the intended flyback primary side switching operation. Troubleshooting and repair of small switchmode power supplies. Switchmode power supply troubleshooting safety the primary danger to you is from the input side of the supply which is directly connected to the ac line and will have large electrolytic capacitors with 320 v or greater dc when powered often, even if the supply does not work correctly and for some time after being unplugged especially if the power. Can someone look up the schematic and walk through the circuit and tell me what other components may have blown. Secrets of smps repair and troubleshooting switch mode power. Those experienced electronic repairers know that having the right procedure to troubleshoot and repair power supplies is the key to longterm success look, if you have a wealth of knowledge regarding switch mode power supplies theories, but no practical on repairs, what good is that. It would save time from me unsoldering parts just to test them. Switching power supply technical manual adm instrument. Apr 02, 2017 the repair of switch mode power supplies smps is economically a good investment for electronics repair shops and for hobbyists. Power supply sequencing reverse power supply battery not all power supplies are created equal. On my board there were 2ea 2200uf capacitors that were bulging. How to repair a switchmodepowersupply smps homemade.
The working principle of switch mode power supply is different from the linear type. Repairing switched mode power supplies smps all about. In case of power off, users can carry out maintenance by visual check, smelling, asking and measuring. Acopian power supply repair acopian power supplies. Yaesu fp29 power supply stopped working qrz forums. In the mean time, i have a mfj 4245mv switching power supply on my desk.
The power supply acts as a stepdown transformer converting high voltage ac into 5, 12, and 3. Repairing switching mode power supplies audioxpress. This kind of big dynamic range can pose a problem for the eightbit digitizing scopes common in electronics labs. Whatever you prefer to call it power supply, rectifier, power system, power module, power brick we make millions of different kinds that can be used in thousands of different applications including electronic equipment, manufacturing, machinery, process control, factory automation, astrophysics, chemical processing, telecommunications. Unfortunately, smps are a bit tricky to repair and i often get asked for advice. Mode power supply reference manual should prove useful. Again this means that, for a given amount of power output, smaller and cheaper transistors can be used, than in similarly rated linear power supplies. Troubleshooting these circuits without a manual can be a real. Troubleshooting switch mode power supplies giangrandi. It also provides practical, useful procedures to follow when you are troubleshooting switchedmode power supplies. Mar 12, 20 uncover battletested switch mode power supply repair strategies by downloading this allinclusive smps troubleshooting manual thats stuffed with color photos.
Switching power supplies are available at mouser electronics from industry leading manufacturers. Repairing samsung la40r81bd 40in lcd tv power supply. Most of them are flyback, regulated, smps but not all. Comments on smps capacitor discharging and testing with series. Be careful not to exceed the voltage ratings of any components on this node. Getting into the power supply repair field is not hard. How to repair a switching switch mode power supply. Switching power supply repair guide repairing the switching power supply can be processed in two steps. Smps repair guide switch mode power supply repairing tips. A switch mode power supply is a power converter that utilises switching devices such as mosfets that continuously turn on and off at high frequency. The power supply used on the pc uses an even better approach. Also using a square wave to drive the switching transistors switched mode operation ensures that they dissipate much less power than a conventional series regulator transistor. The shown unit is a cheap readymade chinese make smps circuit.
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