The user sent a Hisense LCD TV model TLM3233N (motherboard number 7.820.996A), reporting that the TV needed to be powered on multiple times before it would turn on. I personally tested the unit and found that the 5V power supply was normal, but other voltage groups had no output. Testing the STB switch machine control terminal showed a low signal, indicating the motherboard was in standby mode.
I focused on testing the motherboard voltages: -5V, 3.3V, and 1.8V were all within normal ranges. At this point, the maintenance process became challenging. I searched online for the motherboard and found that it could be purchased for as low as 50 RMB on Taobao, which is quite cheap. However, the customer was in a hurry to use the TV and insisted that we should try to repair it instead of replacing the board. How could we demonstrate our technical skills in such a situation?
To avoid a direct replacement, I decided to look into other common failure points. I tested the reset transistor Q7 and found that the C pole was at 0V during boot and remained at 0V constantly. The B/E junction had around 3V, which suggested there was no proper reset signal. After replacing the capacitor CA14, the issue was immediately resolved.
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For reference, here's the schematic file for the Hisense TLM3233H (996A board) LCD TV: LCD color TV circuit schematic.rar