Sunday, December 6, 2009

LCD Monitor Repair

A customer dropped off a Samsung SyncMaster 204T monitor for repair earlier this week, the display flickered and then went dim. He was told by his "computer guy" that the monitor needed a new CCFL. I told the customer I would look at it and that I thought it was more likely to be an inverter circuit issue. After opening the monitor as usual the first thing I did was look for loose connection and bad electrolytic capacitors on the SMPS board(bad electrolytics cause all sorts aof problems and are often the cause of failure), in this case the SMPS and inverter are integrated into one board. Right away I found that 2 secondary filter capacitors in the SMPS that had an ESR of 6 ohms and had changed value from 820uF to 10uF. Both capacitors had a max working voltage of 25V. After looking over the rest of the monitors circuits and checking the components in the inverter circuit I found no other problems. I re-soldered the HV transformers and MOSFET ICs in the inverter circuit as there was a few pins on the ICs with ring cracks as well as the HV transformer pins. I replaced the 820uF 25V capacitors and put the monitor back together. After setting it up and turning it on it was as good as new.I called the customer and told him he could come pick up his monitor. The customer was very pleased and the service charge was only $60. Hope this helps some of you they may come across one of these monitors with the same problem.

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