TCL rear projection TV HW42A61 convergence abnormal maintenance example - Appliances

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A TCL rear-projection TV HW42A61, according to the user, the machine is not clear, it has to be played for half an hour to be clear. Once heard, I am happy, take the tube seat and go to the door for repair.
When I entered the door, I was rear-projection TV. I observed that it was not a socket problem, the image lines were clear, but the three guns gathered in either H or V, and the convergence circuit did not work at all.
Open the cover to touch 392-040, both pieces are cold, the whole machine has no smell, the measurement is no power supply, listen carefully to the regular "吱吱" sound, the original concentrated power supply is here.
Measure +15V (normal), +25V (none), -18V (none). Observe +15V for the board relay control voltage, turn on 220V~, +25 and -18 for the board output. Observe that the appearance of the board is normal, and the measured load resistance is also normal. It was found that the -18V was moved when the primary capacitor was discharged to the end after the power was turned off, and the +25V wire was not moved, and the same was true after the capacitor was replaced. When the load is unplugged and the board is forced to be energized, the board can be started, but it is slower, measuring +25V is normal, while -18V is -35V. Look at the circuit, +25V is the source of regulation, there is a resistor to do the load, and -18V does not, so the voltage is higher, but it is strange that the difference is so large. (It was later found that it was not -18V, but -25V, the domestic machine circuit printed error).
Analysis is that the circuit has insufficient load capacity. Visually, there is an electrolytic capacitor in the primary. First, take it to open the knife. There is no abnormality in the external view, but the capacitance meter is measured, only 6.22 microfarads are left, and a new 10 microfarad capacitor is replaced. When the power is turned on, there will be a stable output immediately, and there is no multiple start sound that has been issued before the no-load.
The installation is powered and the image is back to normal. Measuring the board output +25V (of course, stable +25V), -18V (actually stable -25V), TCL's factory personnel are too irresponsible, actually put the voltage wrong, this will let the maintenance staff Take a lot of detours. After a few minutes of testing, the aggregation module warms up normally. After half an hour of installation, everything is normal. By the way, the three acceleration poles are recalibrated. The color is somewhat reddish and the corners are adjusted.