with acantophis3rd and asgaard2000
Troubleshooting Samsung 153V LCD power supply is just like troubleshooting those crt type. This monitor came in with no power symptom. If you are first time repairing this type of power supply, I recommend you to first remove the switch mode power transformer. Then test every single component in the primary section, before you continue to check the secondary section. You have to be good in testing basic electronic components in order to detect the fault.
You can always browse through my website just in case you do not know how to test basic electronic components. If you do not know the right way to check, you might miss out a bad component and this will lead you not able to solve the problem. After carefully checking all the components in the power supply section, I found the filter capacitor do not have any reading using digital capacitance meter (open) , the two round type fuse also open circuit, 1N4744 15 Volt zener diode short circuit and lastly the power ic TOP247F blown! Testing the switch mode power supply primary winding with a dick smith flyback tester shown green bar which indicated good winding.
What we left here were the secondary diode and filter capacitor. Upon checking them with analog meter and esr meter, found all of them to be good condition. Other area like main board and inverter board also looks okay (Power failure rarely affect these two circuit). Now we have confirmed that only five components found to be faulty. One by one the components were replaced (except one fuse) and just before you switch on the power supply, make sure you connect a 100 watt light bulb across the live ac line-refer to the photo at my website. Once it is done you can then proceed to switch on the LCD monitor to look at the brightness of the bulb.
If it very bright, this suggests that there are still short circuit somewhere in the power section. If it dim or totally goes off, you can now place your red probe to the secondary side to check if any dc present at their respective line. If there are DC voltages present at the output, you can switch off the power, discharge the filter capacitor (for safety purposes), remove the light bulb and connect back the new fuse to its original location.
You are now hundred percent sure that the LCD power supply won’t blow once you switch it on. By the way the filter capacitor is rated at 105 Celsius and you cannot replace it with the 85 Celsius type otherwise it may open up again after using for couple of weeks or months. The ventilation in LCD monitor is not as good as the cathode ray tube monitor, because the power supply is fully covered by a large aluminum plate and it can get hot pretty fast. Conclusion, whether you are repairing Samsung 153V LCD power supply or other brand of LCD monitor, the procedure is the same. Who knows the power problem in this monitor is a common fault and in the future you can tackle this brand of power supply in the shortest time. To measure electronic components is not that difficult, but to get the original parts like the power ic will consume you lots of time.
demonstration of repairing a power supply for a Rhodes Piano
It is very important to know the power supply repair safety before you begin to dismantle the equipment. If you accidentally caused a small amount of current to flow through your body, you may get a shock and even death! Always be alert when deals with power supply. Understand how electricity and power supply work can help you to avoid from electrocuted. Always wears a rubber shoe and have an isolation transformer in your technical department or working area. You may find out more information about isolation transformer by searching on the internet.
If you want to check the hot section in a power supply, always use the one hand ‘rule’ so that it would not complete a path for current to flows through your body just in case if you were to accidentally touched a live connection or cable. If you are tired and weak, do not repair any electronic equipment or else you might end up causing more problems for the equipment by replacing a wrong component. Take a break and come back to tackle the problem when you are fresh again.
Always use original part numbers for replacement when dealing with components in the critical section such as the fuse area. If the fuse rating is 3 ampere, then you must replace it with the same value which is 3 ampere. Sometimes a slightly higher ampere such as 3.15 ampere may be acceptable. Do not use a 10 or 15 ampere for replacements otherwise fire may occurred due to over current because the fuse may not melt.
The main filter capacitor with a high capacitance and voltage must be installed in the correct location. The positive marking at the capacitor must be inserted to the hole where it printed (+) and a negative marking to (-). A wrongly installed filter capacitor can cause the filter capacitor to explode and may injure your face if you are near to it. In some severed cases, the blown capacitor may burn the power supply as well.
Lastly, don’t because of this information explained above scared you away from repairing a power supply. Just make sure you understood the power supply repair safety first and things will become easier. Understanding the safety procedure above can protect your life.
This is a video HOWTO on repairing common power-up failure on Samsung 52 flat screen flat panel LCD television. This video demonstrates how to remove back panel of display, remove power supply board, and replace faulty power supply electrolytic capacitors using a soldering iron.
Repairing a 5 Pin Suitcase Rhodes Power Supply. www.vintagevibe.com