There are only 3 days left until New Year’s Eve, so I want to wish everyone a Happy New Year in advance!
With only a few days left until the New Year, things have been getting busier. This afternoon, a TCL 32-inch TV was delivered to me with a fault described as “three no’s”! After initial analysis, I suspected a 5V standby issue. Upon disassembly, it turned out to be indeed a standby issue with no voltage, but it was a 3.3V standby! I informed the user about the power supply problem and quoted the prices for red, gray, and brown options. The user agreed to the price as long as they could watch TV on New Year’s Eve!
There appeared to be no burning, and the capacitors looked fine. There was no short circuit, and the standby module was FSQ510320V with normal VCC12V. FB3V was oscillating, and there was no short circuit on the secondary side, but there was no output. It seemed that the FSQ510 was faulty, but I didn’t have that model on hand. I asked Baidu, and it suggested that I could use FSQ0265 as a replacement, but again, I didn’t have it. Baidu didn’t provide a clear replacement method, just mentioned modifying the circuit. Some experienced technicians simply replied that these parts are common, and the original ones are not expensive, so why bother with replacements? I found such responses irresponsible and countered by asking if they had all the necessary parts. Repairing is inherently flexible and variable!
With no other options and considering the cost, I decided to explore any alternatives. After checking the FSQ510 circuit, I found it to be quite typical and simple.
Then I looked through the parts box to see what modules I had.
Among all the modules, I felt that Q100 was the simplest, but upon opening the box, I found it was missing. I continued searching for the simplest circuit. In the end, I locked onto the VIP22A. Here’s the circuit:
Once I decided to make the modification, I bent all the pins of VIP22A’s pin 568 so they wouldn’t go into the circuit holes, and soldered pin 7 together. I bent pin 34 so it wouldn’t go into the circuit holes and then connected pin 3 with a wire to the phototransistor collector. The phototransistor collector was originally grounded, so I cut the line there and added a 104 capacitor in series! Pin 4 of VIP22A was connected with a wire to pin 5 of the original circuit and continued to the collector of the phototransistor, while a short wire in the original circuit was disconnected. The modification was completed!
After powering on, the 3.3V output was normal. After rebooting the TV, it returned to normal operation, and the repair was completed! (Note: Not a single original circuit component was removed; only the grounding line of the phototransistor was cut, and a 104 capacitor was added on the back. This replacement is quick, and even if it fails again, it’s easy to restore the original circuit with the parts!)
In fact, nowadays, the standby circuits of LCDs have become modularized. Repairs may not always have all the parts available, so flexible replacements, slight circuit modifications, or using a universal module, or even the most straightforward method of using a mobile phone charger as a standby source can also work.
Original text: http://www.jdwx.info/thread-719459-1-1.html
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