High frequency probe, high frequency line can be customized with other specifications

Photocoupler

Repair Tips for Changhong Color TVs: A Comprehensive Guide 1. For the LA7688N decoding block in the Changhong series, if it shuts down, remove the Y board (viewing board) and back-weld a 4148 diode on VD611 and VD612, connecting the positive of VD613 to the B pole of VD617. 2. In the case of the Changhong 29A18 model where the line size is not full, the main power supply only provides 75–85V. After checking, VD520 was found to have poor performance, so replace RU2. 3. For the Changhong CK56B2 (22") model, if the field vibration occurs and the voltage at pin 33 of TA7698 is only around 4V instead of +8.6V, check for open circuits in the push tube or transformer. 4. On the Changhong 2939FD model, the upper part of the screen has a sweep issue. Enter the "S" bus and return to ABK--ENABLE. When the fault occurs, brightness becomes too bright. Check the comb filter and re-solder if necessary. 5. For the Changhong N2918 model, there's a blue background without picture when using AV input. The AV output has no image but has sound. Adjusting the fine-tuning allows sound, but the TV sometimes has sound and a blurry image. After investigation, the comb circuit was faulty. Re-soldering resolved the issue, likely due to capacitor leakage. 6. In the Changhong C2589 model, black lines appear in the upper part of the screen. After repeated heating checks, the C329 (471K polyester capacitor) was found to be bad. Replacing it restored normal operation. 7. The Changhong C2191 model emits a "吱" sound and doesn't work. Unplugging the deflection coil shows that the line C voltage is normal. Upon inspection, C428 (1UF/250V) was shorted, and replacing it fixed the issue. 8. The Changhong C2992 model shows jagged images in the upper part. Checking C825 (field supply capacitor) revealed it to be 35V/1000UF and functioning normally. 9. For the Changhong G2125 model, the upper half of the screen length was found to be abnormal. Replacing R402 (120K resistor) resolved the issue. 10. The Changhong 2118FA (A6 movement) model had VD514 (4148) open circuit. The main power supply was normal with a dummy load, but the tube burned after 2 seconds under load. 11. The Changhong C2919PK model had power indication and standby 50V, but failed during boot-up. The line output load (pin 7) VD408 (RU4Z) was shorted. Replacing it restored normal function. 12. The Changhong G2132 (K) model showed power indication but no secondary boot. The line wasn’t heated, and the main load was 130V with a dummy load. After multiple checks, the deflection coil was found to be shorted. 13. The Changhong R2916N (and R2518N) model had a line center shift to the right by 3 cm, no characters, and AV also no picture. D403 and D404 were found to be shorted. Replacing D404 (5.1V) fixed the issue. 14. The Changhong 25K18 model with LA7841 field block showed upper compression and lower thinness. Replacing C301 (1000P) solved the problem. 15. The Changhong G29K36 model had a bright line. N30 (LA7841) was faulty, and VD302 (1Z75) voltage regulator tube was checked for short circuits before replacing LA7841. 16. The Changhong 25N16 model had a 10 cm map compression and rolling. Replacing C302 (10N) resolved the issue. 17. The Changhong C2919PK model had upper retrace lines. Replacing C318 (35V/220UF) and C305 (50V/1UF) improved the condition. 18. The Changhong C2919PS model had stripes and a "black" sound (blue background off). The comb circuit was faulty. 19. The Changhong C2588A model had rare compression failure. Replacing C317 (2.2UF) fixed the issue. 20. The Changhong C2169 model had a red "M" character fault. This indicates entering debug mode. If remote control cannot turn it off, press an unused button between “SYS1/SRC” and “AN-SEL” on the K1L remote to change the color to green. 21. The Changhong C2169 and similar models may start in AV mode. This indicates a program change, usually due to memory or external circuit issues. 22. The Changhong R2518AE (D) model had instructions but could not be turned on twice. It burned the tube. After checking, the line frequency 15625 was causing the issue. Replacing VD431 (1N4148) fixed the problem. 23. The Changhong C2588PS model had small retrace lines. After checking, the field blanking was bad. Replacing R321 (2.2K) resolved the issue. 24. The Changhong C3419PS model had a 5 cm retrace line. Replacing C318 (bad) fixed the issue. 25. The Changhong R2518AE model constantly burned tubes. Replacing C436 and C435RO (if they are CBB81 type) and the tube restored normal function. 26. The Changhong 2938FD model had no sound. No 16V was present, and 872 (0.27/0.5W) resistor was open. Replacing it with 1W/0.33 resolved the issue. 27. The Changhong R2519N model automatically shut down. R820 (0.15 ohm) had deteriorated to 0.5 ohms. Replacing it fixed the problem. 28. The Changhong 2518FN series had upper length and lower compression. The bottom had 3–4 cm of no light. Replacing C306 (4700/25V) fixed the issue. 29. The Changhong R2519N model with TDA6103Q had slightly brighter brightness. R421 (100K) increased in resistance. If the boot was bright, RX19 (220K) was opened. 30. The Changhong D2962A model had three no issues. The line had been worn, and C461 (7200P/1500V) was degraded. Replacing it restored normal function. 31. The Changhong G2536 model had no saved table. Closing the blue background allowed fine-tuning to save settings. AV map flip occurred. Checking CPU pin 36 (C022--101N) showed normal 3.5–4.5V. 32. The Changhong T2981 and T2982 models had picture differences. Check the antenna input amplifier box and cross-line tuner and antenna input box. 33. The Changhong SF2915 model had power indication but no boot. CPU (N100) had only 2V instead of 3.3V. Replacing V871 (C2688L) fixed the issue. 34. The Changhong 2588K model burned the line. The new line had small pressure. Replacing C472 (7200P/1600V) on the pillow board restored normal function. 35. The Changhong C2919PK model had some channels running after a few minutes. Checking the middle of the main box revealed a bad component. 36. The Changhong C2919PS model had irregular running. Cracks were found at the main high-frequency head pin. Re-soldering fixed the issue. 37. The Changhong 2118FA model burned the tube V432 (D1651). Power supply and capacitance were normal. VD441 (RM11C diode) was shorted in the deflection circuit. 38. The Changhong G2125 model had instructions but did not boot. 18V power supply had a short circuit. V832 (D400-E) was bad, burning D834, D835, and R824. Replacing them fixed the issue. 39. The Changhong SF2551 model had three no issues. Replacing N801 (STR-F6454), VD830, VD808, and V801 (C2655) restored normal function. 40. The Changhong C3419PD model lacked Y signal. The clarity enhancement box was faulty. Shorting pins 1–3 provided emergency troubleshooting. 41. The Changhong H29D80 model had poor sound. Z608 {L6.5C} was faulty. Replacing it restored normal function. 42. The Changhong G2985 (B) model had line distortion, left and right difference of 1CM. Replacing R931 (0.5W15 Europe) with 150 ohms fixed the issue. 43. The Changhong C2152 (KV) model had LA7680 for small signal, with instructions, and auto-boot after a few minutes. Replacing C563 (35V/330UF) fixed the issue. Wood grain interference was handled by replacing C562. 44. The Changhong T2982 model had power indication but no boot. VD408 (RU4Z) was faulty. Replacing it restored normal function. 45. The Changhong C3419PD model had normal standby but burned C4706 adjustment tube. The 400V/560UF capacitor was faulty. Booting produced a "beep" sound. 46. The Changhong C3419PK model had 115V main power supply dropping to 100V. R868 (270K/1W) was open. Replacing it fixed the issue. 47. The Changhong HP series rear projection power supply improvement involved changing R888 from 270K/1W to 470K/1W. A 0.22UF/250V capacitor between VC801 (2)-(3) feet reduced "吱" sound and interference. Additional Tips: - For A6 movement color TVs, when overhauling or repairing TDA7496 without sound, connect CRT, speaker nets, and main board ground with the screen line. - For noise problems in certain models, adjust the E pole resistor R115 (0.01UF) in the front intermediate frequency amplifier. - When a color TV displays a green screen after turning on color saturation, check the LA7688 and LC89950 circuits. - For A6 movement 21-inch TVs with frequency drift, replace the original CPU with CHT0408-5L21. - LA7688A can be replaced with LA7688B, and back-solder capacitors to prevent damage. - For CN-5 movement, check AN5095 (20) foot voltage and ensure correct components are used. - For CN-5 movement power inductor L801, 2.2uH can be used as a replacement. - For CN-5 movement field "嗡嗡" noise, replace C675 with CD288H-16V-2200uF. - For stability improvements in CN-5 movement, replace resistors and capacitors as specified. - For CH-10 movement, use specific MOSFET replacements and avoid mixing crystal types. - For CH-10 movement, adjust resistors and jumpers to resolve boot and display issues. - For some color TVs, increase resistance and modify diode connections to fix character jitter. - For local station reception issues, adjust signal modulation and reduce R206 resistance. - For G2985 models, BSC68H2 and BSC70E2 are interchangeable. - For V840 damage, replace VD873 with BYM26D to eliminate the issue. - For karaoke signal issues, use two sets of 2CK75D diodes to stabilize grounding. - For NC-6 movement, replace R123 and C125 to fix channel issues. - For G2966B model, adjust OPT0 and OPT1 for proper data display. - For NC-6 movement power supply, discharge C810 with a 10K resistor before repair. - For G2967A model, check clamp diodes and speaker wires for issues. - For sawtooth interference in NC-6 movement, replace L442 (TLN3063).