Shorted SMPS Transformer
Few days ago my company received 4 units of HP7500 17″ CRT Monitor for repair. I was told that these four Monitors was from a school. They had about more than 10 over units that have the similar problem which is no power. According to them all of the bad Monitors were hit by lightning strike! They just wanted to test the four units out to see whether it could be repair or not. If yes then they will send the rest of the faulty unit. My staff have checked all of the four Monitors and all turned up to have the same problem where all of the SMPS transformers have a shorted primary winding! I have confirmed it myself too when i used the flyback/coil tester to test it out. The LED bar doesn’t lit at all indicating a severe shorted turns in the primary winding.
Since SMPS Transformer are quite difficult to rewind and third party rewinder not interested in rewinding small transformer and furthermore there are no suppliers selling this part i told my staff to pack up the Monitor and return the set to the customer. For your information SMPS transformer usually are quite reliable but i guess i got to spend some time to analyze how to rewind a SMPS transformer just in case if there are similar cases again. Obviously at the beginning there must be lots of obstacles but I’m sure one day i will be able to rewind one.