23 cases of Changhong rear projection TV repair experience sharing - Home Appliances

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1, DP4888 three no, remove the power board, found N801. (STRF6658B) burst, the fuse has been blown, after testing VD821 breakdown, VD802 is not worn, C820.450V/820UF loss of capacity, replace the above components boot everything is normal.
2, DP4388 convergence is poor, try to enter the maintenance state for debugging, green and green two guns can be adjusted, only the red gun convergence can not be adjusted longitudinally to replace the convergence components, everything is normal.
3, DP4888 convergence is poor, red convergence is constantly changing, suspected of high-voltage fire caused by the inspection, no change, replace the convergence of components repair.
4, DP4388A three no, remove the power board, found that the fuse is blown, the fuse inside is black, prove that the power supply part has a serious short circuit, the test N801 (STRF6658B) has been broken, and then measure VD802 (C2655), VD821 (0.5W/18V) Breakdown, C820 450V/820UF lost capacity, replace the above components to repair.
5, DP5188 protection immediately after the second boot, first suspected that the projection tube damage caused protection, in turn disconnect the red green blue viewing board, when disconnected Lanshi board, the second boot with high-pressure ignition sound, determine this The fault is caused by the damage of the blue projection tube, and the replacement of the blue projection tube.
6, DP4888 convergence will change the slope every few days, change the assembly of the assembly.
7, DP5188 horizontal bright line, open the back cover of the machine, found that the C379 (63V/10UF) capacitor was broken after being replaced, N301 (TDA8351Q) was also replaced, the horizontal bright line after the start, the field supply voltage +45V normal, Test N3013 foot no +18V voltage in the test R370, VD70, R380 When the R380 is measured, it is found that the R380 resistance value becomes larger, replace the repair.
8, DP4388 (01) does not boot twice, remove the power board RF855 resistance value infinity, replace repair
9, DP4388 (01) convergence can not be debugged, suspected that the convergence power supply is damaged, resulting in the convergence module can not work properly, the measured C3852 (V502) 5000 (R553) / SOC resistance are damaged, after the change everything is normal.
10. DP4888 is sometimes not in the left channel. The C909 (50V2.2UF) capacitor pin on the mode AV board is short-circuited to the ground. The printed board is engraved with a small knife (between the printed board and the capacitor pin hole).
11, 51PT28A secondary boot protection, the indicator light is red after booting, remote control boot, line protection after instant start, boot judgment is a problem with the protection circuit or other circuits, after the V491 disconnected, the boot fault remains, then measure VD491 normal , VD492 breakdown guide, protection circuit work, replacement repair.
12. There is a purple vertical line in the middle of DP5188. It is suspected that the projection surface is burned. The red and green blue projection tube is covered by paper in turn. When placed on the green projection tube, the purple vertical line disappears and the green projection tube is replaced.
13, 51PT28A does not start, the green indicator light is on, measured TDA8844 (40) pin voltage is 8V, indicating that TDA8844 does not start, the bus voltage is basically normal, TDA8844 power supply pin is also normal, power board voltage is also normal, suspected line oscillation time constant There is a problem with the capacitor. Note: 9-pin capacitor. For C230 (1U/50V) C299.4n7 capacitor, the test machine is normal.
14, DP5188 (01) secondary non-boot protection, measured each output voltage is basically normal, suspected that the projection tube is damaged, the RGB tail board is removed in turn, the fault remains, and the capacitance of the relevant circuit of the Y board is normal. The potentiometer is turned on normally.
15, DP5188 green gun defocus, try to adjust the focus voltage is normal. But when the brightness is increased, the image has green chrome, suspected TDA9332H processing is problematic, change the TDA9332H fault remains, so only the projection tube has problems, there are high voltage branches There is a problem with the box and the focus potentiometer. The projection tube and the high-voltage branch box are still faulty. The repair is in a state of necessity. After the analysis, the acceleration voltage and the focus are not adjusted, and the maintenance status is changed to the RGB three-gun acceleration pole. The voltage and focus voltage are debugged, and then the maintenance state is exited, and the image is restored to normal (suspicion of the focus potentiometer and the accelerating potentiometer, there may be quality problems), causing voltage instability and defocusing)
16, DP4388 no characters, the image of this machine is normal, but there is no character. It is suspected that the character module PCA8516 and the line signal D/A block HIC157 are faulty. In order to reduce the fault range, the PCA8516 fault is still replaced first, then the HIC157 is replaced, and the TV is turned on. The machine returned to normal.
The block diagram of the line signal processing is as follows:
17, DP5188A boot protection, open the back cover of the TV, immediately protect the boot, listen to the line has a sound of the line, indicating that the high-voltage part of the machine has a short circuit, open the high-voltage branch box and the motherboard connection socket, respectively Measuring the resistance to ground, a set of high voltage and ground resistance is 7.3KΩ, a set of 180MΩ, indicating that the high voltage branch box is shorted to the ground, causing high voltage output protection, replacement repair (high voltage branch box normal ground resistance value is a group 340KΩ, one set is infinity)
18, 65PDT18 three no, open the back cover, remove the power board measured 300V normal, but no output voltage, suspected output voltage has a short circuit fault, causing current overcurrent, damage RF853, check 16V related circuit, found V881 (C3852) C , E wears, replaces the boot, everything works.
19, DP4388 boot image is normal, after a while, the stripe interference line begins to appear. First, the hand beats, the interference line flashes with the hand. It is suspected that there is a bad solder joint or high voltage line contact in the high voltage part. Check the high voltage part carefully, and listen carefully. The presence of the interference line hummed, and the scanning board was removed and carefully examined. It was found that the N510 (TPA6032AH) had different degrees of cracks on both pins, repair welding, mounting, testing, and the TV returned to normal.
20, DP4388A boot three minutes appeared three no, suspected power failure, remove the power board, found that T801 below the printed board break, there is a mark between the copper and platinum, connected to watch the TV back to normal.
21, DP4388A boot protection. First of all, it is necessary to distinguish the power-on protection is the power supply protection. The high voltage part is faulty. The high-voltage part is disconnected first, the power is turned on, and the protection is not indicated. It indicates that the high-voltage part is faulty. Try to replace the high-voltage branch box and start the test TV to restore normal.
22, DP4888 map flash, there is an image when changing channels, this fault is similar to the line is not synchronized, carefully observed, this machine has no characters to display, analysis only the line synchronization public part failure, in order to cause the two faults occur at the same time, try to change HC7157, Boot, the image returns to normal.
23, DP4388 image is not normal, the automatic search image is not normal, use the manual search image can be normal, change TDA93217 (8) foot, parallel inductance T101 after normal.