**Leakage Current at the Antenna Terminal of Hisense TC-2125C TV**
### Fault Phenomenon:
Leakage current at the antenna terminal.
### Fault-related Circuit:
Demagnetization circuit.
### Fault Location:
Leakage from the demagnetization coil.
### Analysis and Troubleshooting:
Using a multimeter with the R10kΩ setting, the isolation resistance between the power plug and the metal casing of the high-frequency head was measured to be 200kΩ. Under normal conditions, this value should be approximately infinite. This indicates that there is leakage between the hot ground and cold ground isolation components, with C531 and C532 being the most likely culprits. After desoldering one end of C531 and C532 and re-measuring the isolation resistance, the value remained at 200kΩ. Upon checking, R531 and R532 were found to be normal. The photo-coupler VD515, auxiliary transformer T581, and switch transformer T551 (all isolation components) were removed and the isolation resistance was remeasured, but it still remained at 200kΩ. Suspecting leakage in the circuit board, further investigation did not reveal any leakage points.
Upon observation, the demagnetization coil was directly mounted on the picture tube. If the demagnetization coil leaks to the graphite layer of the picture tube, the same fault could occur. After unplugging connector XP1 and re-measuring the isolation resistance, the value returned to infinity. A new demagnetization coil was installed, and the previously disconnected components were resoldered. After testing the unit, the fault was resolved.
### Source:
Beijing Hisense TV Repair Center
http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3764590