Skyworth 37K05HR after 10 minutes of booting black screen (no backlight) sound repair case: UV Film,UV Screen Protector,UV Curing Screen Protector Shenzhen Jianjiantong Technology Co., Ltd. , https://www.jjttpucuttingplotter.com
Power board number: 168P-P37ALK-02
This machine is a rework machine and has been repaired elsewhere for several days without results.
Fault phenomenon and analysis ideas:
The sound of the boot image is completely normal, about 10 minutes or so, the black screen has no image but the sound is normal.
Turn off the phone and turn it on immediately. It is also a black screen for about ten minutes. It feels like "timed".
This phenomenon firstly eliminates the problems caused by overheating of components. For overheating, the time should be shortened. There are several reasons for this black screen.
Such as: poor solder joint contact, overheating (excluded), poor component stability, protection circuit problems.
Open the cover check, whether it is normal or black screen, the power supply 5V, 12V, 24V, etc. are normal.
Going back to the road, there is no output when the black screen is high voltage. Most of these faults are on-screen lights.
Or the long-term performance change of the high-voltage transformer causes the wrong protection.
The backlight oscillation circuit IC of this machine is STR-H3435, by changing the pulse signal input by 8 feet (used to determine the core chip pulse frequency),
Change the reference setting, that is, control the internal voltage comparison threshold of the IC through the size of the 8-pin external resistor to change the misjudgment of the protection circuit.
The actual circuit transformation: the scheme 1. It can be realized by adding a 6.8K resistor in front of the 8-pin R25 (33K). Scheme 2. Remove R24 (120K). Only choose one of the two options.
The above maintenance cases are for reference only, please analyze the specific situation.
Part of the physical map:
Reconstruction icon, only one of the two places,
This repair only solves the problem by removing R24 (identification 124, 120K).
Note: R25/33K, R24/120K are connected in parallel
June 20, 2023