T-CON Board Repair: FIX Missing Boost Voltage (VGH/VGL/AVDD) | Level Shifter IC Replacement
T-CON Board Repair: FIX Missing Boost Voltage (VGH/VGL/AVDD) | Level Shifter IC Replacement
In this detailed tutorial, we tackle a common and challenging T-CON board repair where the crucial Boost Supply voltages (AVDD, VGH, VGL) are completely missing. This fault often leads to symptoms like a blank screen, lines, or flickering in the display.
Follow along as we precisely diagnose the failure and successfully perform a replacement of the faulty Level Shifter IC (specifically the s301 a21) on an AUO panel T-CON board. This video is a must-watch for technicians looking to deepen their DC-to-DC circuit repair skills and get a board back to a fully working condition!
Video Timestamps
Timeframe Description
0:00 Introduction & Problem Diagnosis: Identifying the core fault—the DC-to-DC IC is not producing the higher Boost Supply voltages (VGH/VGL/AVDD).
0:30 Initial Power Consumption Test: Connecting the T-CON to a power supply to check wattage and amperage draw for initial fault localization.
1:23 Voltage Measurement (Before Repair): Checking critical voltages like 3.3V, 1.2V, and noting the absence of AVDD (should be ~16V) and VGH (~27V).
2:16 Level Shifter IC Fault Confirmation: Checking the gate signals (LC1, LC2, HC1, etc.) for a short circuit in diode test mode, confirming a fault in the Level Shifter IC.
2:49 IC Removal & Area Cleanup: Removing the faulty s301 a21 Level Shifter IC.
3:24 Post-Removal Circuit Check: Re-testing the signal lines (HC1 to HC6) in diode mode to confirm the short is removed, proving the IC was the cause.
4:09 Safety Warning & Precautionary Steps: Critical advice: always disconnect the FFC panel cable before replacing the Level Shifter IC.
5:20 Voltage Re-Test (IC Removed): Checking the VGH, VGL, and AVDD voltages after IC removal. Notice the increase in power consumption, confirming the Boost Supply is now active.
8:18 New Level Shifter IC Installation: Fitting the replacement IC onto the T-CON board using a specialized PCB holder.
9:32 Post-Installation Diode Test: Final check on the signal lines (LC/HC) in diode mode to ensure the new IC is correctly seated and no shorts exist.
10:37 Final Voltage Confirmation (All OK): Verifying the restoration of all necessary voltages: AVDD (~16V), VGH (~30V), VGL (Negative Voltage), and the switching LC/HC signals.
12:23 Gamma Voltage Ladder Check: Confirming the gamma voltage ladder is also functioning correctly, a sign of a fully repaired board.
13:30 Conclusion & Next Steps: Concluding the repair and outlining the next steps to get the repaired board back to the customer.
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