AVANT Power Supply circuit

Description: The AVANT employs a Switched Mode Power Supply (SMPS), which is centered around a 32 kHz ramp oscillator. This oscillator ceases operation if the overload protection circuit identifies an overload condition. When the oscillator is inactive, the 8-volt standby voltage is not produced, resulting in the red standby light remaining off. It is essential to determine whether the issue stems from an actual power supply failure or an overload within the TV, which causes the power supply to shut down due to the overload protection mechanism. This assessment should be conducted at the connectors on the power supply board. A block diagram illustrating the involved connectors is available. Power should be checked at connector P46 between pins 1 and 2; caution is advised during this process.

The Switched Mode Power Supply (SMPS) in the AVANT television operates on the principle of efficiently converting electrical power using high-frequency switching. The core component, a 32 kHz ramp oscillator, generates a square wave signal that drives the power supply's switching transistors. This process allows for the regulation of output voltage with minimal energy loss, making it suitable for compact electronic devices like televisions.

In the event of an overload, the protection circuit is designed to monitor the output and shut down the oscillator to prevent damage to the power supply and connected components. The absence of the 8-volt standby voltage indicates that the system is in a protective state, which prevents the standby light from illuminating.

To diagnose the issue effectively, it is crucial to differentiate between a genuine failure of the power supply and a fault elsewhere in the television that triggers the overload protection. The recommended approach involves measuring the voltage at the power supply board's connector P46. This connector is critical as it links the power supply to the rest of the television circuitry. By checking the voltage across pins 1 and 2 of P46, one can ascertain whether the power supply is functioning correctly or if the overload protection has been activated due to an internal fault.

Precautionary measures should be taken during this testing to ensure safety and prevent further damage. It is advisable to use insulated tools and, if necessary, to have a qualified technician perform the checks to avoid electrical hazards.The AVANT uses a Switched Mode Power Supply which means the heart of it is a 32khz ramp oscillator which is stopped if the overload protection circuit detects an overload. Without the oscillator running the 8 volt Standby voltage is not generated and is why your red standby light is not on.

We first need to establish if the situation is because of an actual power supply failure or an overload somewhere in the TV which is shutting down the power supply through the overload protection. This is best done at the connectors on the power supply board and below is a block diagram showing the connectors involved.

Check the power at P46 between pins 1 & 2, be very careful