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Key points
• LD67B/LD67C = LG TV chassis, not a single IC.
• Service manuals include full board-level schematics, block diagrams, PCB layouts and part lists.
• Observe copyright and safety rules; LED-LCD TV primary PSU involves lethal voltages.
Chassis identification
• LD67B / LD67C is silkscreened on the main-board PCB and quoted on the rear product label.
• Typical screen size: 31.5 ″ class LED-LCD, FHD/HD-ready, 2015-2017 production.
Schematic structure (what you will find in the manual)
a. SMPS / Power block
– Universal-mains AC input → EMI filter → bridge-rectifier → PFC (≈400 Vdc)
– LLC-resonant converter generating 12 V, 24 V and standby 3.5 V rails (IC: L6599A + NCP1653 or Fairchild FAN7930 variants depending on PCB revision).
– On-board LED back-light driver: boost-type or SEPIC supplying 80 – 120 V @ ≈200 mA to LED strings.
– PS-ON, BL-ON and PWM dim control lines driven from main board.
b. Main board (MB)
– SoC: LGE3610 (ARM Cortex-A9 dual-core) + DDR3 (512 MB or 1 GB) + SPI-NOR/eMMC.
– HDMI 1.4 Rx, MHL, component/composite A-D, EDID EEPROM.
– Tuner/Demod: Silicon-tuner (e.g., Rafael R850) + LGDT-H demodulator (ATSC/DVB-T2/PAL variants).
– Audio path: I²S → class-D amplifier (TPA3110/TPA3116 derivative).
– Scalar outputs: LVDS to T-Con; EDID/DDC level shifters.
c. Peripheral boards
– T-Con: gate and source drivers, gamma and Vcom buffers (e.g., Novatek NT68169).
– IR / keypad, USB Wi-Fi/Bluetooth module in some revisions.
Typical failure points & test locations
• No-power: check standby 3.5 V at connector P201-1; open start-up resistor or faulty U601 (STR-A6100 series).
• Back-light flash then dark: LED-DRV “OVP” flag or open LED string; test LED string with 20 – 30 V CC source.
• No video / logo: 1.0 V, 1.2 V, 1.5 V rails around LGE3610; look for shorted MLCCs or burnt AOZ (buck) modules.
| Cross-references | Chassis code | Screen size | Manual code | File name (Elektrotanya) |
|---|---|---|---|---|
| LD67B | 32″ HD | MFL69494401-REV01 | lg_32lh510_32lh520_ld67b_rev01.pdf | |
| LD67C | 32″ HD | MFL69494401-REV02 | lg_32lh510_32lh520_ld67c_rev02.pdf |
• Unlike older CCFL sets, LD67B/C uses integrated LED driver on the PSU board to reduce BOM.
• Newer LG models (2019 →) migrate from LGE3610 to Realtek RTD or Mediatek MT580x SoCs and from LVDS to V-by-One, making LD67 series documentation still relevant for repair of earlier LED-LCD generations.
• Component shortages have prompted many repair shops to salvage working PSU boards; having the schematic helps doing component-level repair instead.
Why knowing the exact chassis matters
LG re-uses panel part numbers across different chassis. Using a wrong schematic (e.g., LD62A vs LD67B) often leads to PSU pinout mismatches—dangerous for both set and technician.
Obtaining the manual (step-by-step)
• Service manuals are LG copyrighted documents distributed for authorised service. Most sites host them under “fair use” for repair; redistribute only where legal in your jurisdiction.
• Primary PSU carries ≥400 Vdc; strict adherence to IEC 60950 / 62368 safe-work practices is mandatory.
• Use isolated bench supply and differential probe when tracing PFC/LLC stage.
• Pre-power test: disconnect LED harness, load 24 V line with 10 Ω 50 W resistor to avoid OVP trips.
• For firmware corruption (dead boot logo): the SPI-NOR contains both bootloader and NVRAM. Clone from known-good board or flash with LG jig (UART).
• Some early LD67C revisions have different panel voltage (VGH/VGL) regulators; always verify schematic revision against PCB silkscreen (e.g., EAX66751203 vs EAX66751204).
• If your “LD67” is not an LG TV chassis but a component marking (e.g., opto level sensor LD67-NS), this answer will not apply—please specify.
• Study LG’s later LA08 / LA16 chassis to see migration to single-board architecture.
• Look at Onsemi NCP1397 application notes to understand LLC stage used in LD67 PSU.
• For persistent main-board failures, explore JTAG access to LGE3610 (J500 header).
“LD67 schematic” almost always points to the LG LD67B/LD67C LED-LCD TV chassis (≈32″ models). Download the service manual MFL69494401 from sites such as Elektrotanya to obtain full board-level schematics. Use the document to troubleshoot PSU, back-light, and main-board issues, observing safety and copyright constraints. If your enquiry refers to a different LD67 entity, additional context will be necessary.
