Sunday, 25 July 2021

Toshiba 37AV502U LCD TV – service mode, firmware update, SMPS circuit diagram, troubleshooting, wiring diagram

 An isolation transformer should be connected in the power line between the receiver and the AC line before any service is performed on the receiver.

2. Always disconnect the power plug before any disassembling of the product. It may result in electrical shock.
3. When replacing a chassis in the cabinet, always be certain that all the protective devices are put back in place, such as non-metallic control knobs, insulating covers, shields, isolation resistor-capacitor network, etc.
4. Always keep tools, product components, etc. away from children as these items may cause injury.
5. Depending on the model, use an isolation transformer or wear suitable gloves when servicing with the power on.
Disconnect the power plug to avoid electrical shock when replacing parts. In some cases, alternating current is also impressed in the chassis, so electrical shock is possible if the chassis is contacted with the power on.
6. Always use the replacement parts specified for the particular model when making repairs. The parts used in products require special safety characteristics such as in-flammability; voltage resistance, etc. therefore, use only replacement parts that have these same characteristics. Use only the specified parts when the mark is indicated in the circuit diagram or parts list.
7. Part mounting and wire routing should be the same as that used originally. For safety purposes, insulating materials such as isolation tubes or tape are sometimes used and printed circuit boards are sometimes mounted floating. Also make sure that wiring is routed and clamped to avoid parts that generate heat or use high voltage. Always follow the manufactures wiring routes / dressings.
8. Always ensure that all internal wirings are in accordance before re-assembling the external casing after a repair is completed. Do not allow internal wiring to be pinched by cabinets, panels, etc. Any error in reassembly or wiring can result in electrical leakage, flame, etc., and may be hazardous.
9. NEVER remodel the product in any way. Remodelling can result in improper operation, malfunction, electrical leakage, or flame, which may be hazardous.
10. Always perform an AC leakage current check on the exposed metallic parts of the cabinet such as antennas, terminals, screw heads, metal overlays, control shafts, etc. to be sure that the set is safe to operate without any danger of electrical shock before returning the set to the customer.

Connector pin configuration

Internal wiring diagram


Firmware update

Firmware updating for this chassis family is accomplished via a USB port located on the rear of the unit. It is designated as “Service” and is located between the HDMI and PC audio input jacks.

The factory mode, necessary adjustments, and update procedures shown below can be accessed in this unit using the supplied remote control transmitter.  To access the factory mode, you must press “Left Arrow (<), Exit, Enter” in sequence on the remote transmitter. The mode can be exited by pressing exit or simply turning the unit off.


Troubleshooting tables:  Set dead – No or distorted video


No Backlight and No sound troubleshooting


SMPS (Power board) schematic



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