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Nie, dziękuję Przekieruj mnie tamTV TCL 32S615 MT21X7 LIGA TEM 12V 3.3V MESMO COM O DISPLAY DESCONECTADO NÃO TEM TENSÃO DE VGL E NEM VGH
Functional blocks involved
• Main SMPS → 12 V (panel), 3.3 V (logic).
• T-CON power stage (on the MT21X7 board, close to LVDS) → generates
– AVDD ≈ 15–17 V,
– VGH ≈ +24 V,
– VGL ≈ –7 V,
– VCOM, VGREF, etc.
• Control: SoC asserts PANEL_EN / TCON_ON after standby release; this line typically goes high to 3.3 V 100–300 ms after main rails are stable.
Typical converter topology
• One multi-output DC-DC controller (e.g., RT8293, TPS65132, MPQ8633, ISL9860 family)
– Boost section (SW1 + inductor + diode) → AVDD / VGH
– Charge-pump/inverter (CFLY, CP1/CP2) → VGL
• Protection fuse FPxxx or Lxxx (0.5–1 A) on the 12 V feed.
• High-side MOSFET or load-switch (Qxxx) controlled by PANEL_EN.
Failure modes consistent with the symptom
a) Blown SMD fuse / open inductor on the 12 V → T-CON rail → no VIN at the converter.
b) Load-switch MOSFET stuck open because PANEL_EN is low (faulty SoC, bad pull-up, corrupted firmware).
c) Shorted ceramic capacitor on VGH or VGL pulling the rail to ground and triggering the converter’s protect-off.
d) Internally shorted or open DC-DC controller IC – no switching even with correct VIN and EN.
e) Over-current shut-down caused by a gatedriver short inside the LCD panel (your test with flat cable disconnected excludes this).
Recommended measurement sequence (all chassis ground referenced; use isolated bench PSU or differential probe if possible):
| Step | Point / pin | Expected reading | Interpretation |
|---|---|---|---|
| 1 | 12 V at main SMPS output | 11.5 – 12.5 V | confirms PSU OK |
| 2 | 12 V after FPxxx/Lxxx (VIN pin of converter) | same as above | if 0 V → open fuse / MOSFET |
| 3 | ENABLE / PANEL_EN pin (datasheet) | ≥ 2.5–3.3 V when TV ON | if <0.5 V → logic problem |
| 4 | SW pin of converter with scope | 200 kHz–1 MHz switching | no pulses → IC dead or EN/VIN missing |
| 5 | Resistance to GND, VGH node | > 100 kΩ (panel disconnected) | few Ω → shorted cap |
| 6 | Resistance to GND, VGL node | > 50 kΩ | near 0 Ω → shorted cap / IC |
Component examination
• Inspect DC-DC IC for cracks or thermal discoloration.
• Measure Schottky diodes Dxxx (boost) and Dxxx (inverter) for shorts.
• Replace suspicious MLCCs on VGH/VGL (2.2 µF–10 µF/35 V).
• If VIN and EN good yet no outputs, replace the controller IC; hot-air rework is mandatory (lead-free, fine-pitch).
Enabling sequence (captured from service manual snippets available on Elektroda/Electronica-PT)
t = 0 s: AC in → STB_5V → STB MCU
t ≈ 0.2 s: PWR_ON → 12 V / 3.3 V rise
t ≈ 0.4 s: PANEL_EN high → T-CON converter starts → AVDD, VGH, VGL appear
Any break in this timeline kills VGL/VGH.
• MT21X7 family integrates part of the T-CON to save cost; failures of its tiny power block (often a 3 mm × 3 mm QFN) became more common after 2022 due to aggressive BOM reduction.
• Replacement boards (part-no. 40-MT21X7-MB3 or MB5) are readily available on Asian marketplaces (< US$25).
• Some repairers re-implement the missing rails with an external “universal T-CON booster” module, but this is considered a temporary fix.
– VGH is generated by boosting 12 V through an inductor; VGL is created by an inverting charge pump referenced to the same boost node. If either switching network is silent, both rails disappear because they share the same controller.
– The fact that the rails are absent with the display unplugged tells you the converter never started (Enable/VIN fault) or latched off immediately due to an on-board short – eliminating the panel as the load.
• Board-level troubleshooting exposes you to mains potential on the primary SMPS side; isolate and discharge before probing.
• Respect manufacturer IP; service manuals found online may be subject to copyright.
• Ensure ESD precautions to avoid damaging the SoC or eMMC during soldering.
• If PANEL_EN is missing because of corrupted firmware, a board re-flash can revive the set; however, this is rare.
• Some MT21X7 revisions use a separate daughter-board T-CON; instructions above still apply but physical location changes.
• If both AVDD and VGH/VGL are missing, suspect upstream fuse/MOSFET first.
• Retrieve the schematic “TCL_MT21X7_MB3_Rev1.x.pdf” from Electro-Tanya or ElektronicaBR for exact test-point IDs.
• Review application notes AN-1421 (Richtek) on multi-output TFT-LCD power to understand protection behavior.
• Explore use of programmable gate-driver ICs (e.g., TI TPS65150) as retrofit if the original QFN is obsolete.
Your TCL 32S615 boots, but the gate-drive rails VGL/VGH are dead because the small DC-DC/boost converter on the T-CON section never starts or is being starved of input or enable. Verify 12 V feed and PANEL_EN, replace the protection fuse/MOSFET if open, then the converter IC or any shorted output capacitor. Once VIN and EN are restored, VGH (~ +24 V) and VGL (~ –7 V) will re-appear, allowing the panel to operate.
