Vermes
Advanced Member level 4
This device was based on AVT 2671 design. It is very important to provide enough cooling to the TDA 7294, so this device uses not only normal fans, but also special feet of the system. The surface of adhesion to the heat sink is 2,9 cm sq, while with 15 feet that surface is reduced to 0,6 cm sq. The system is screwed to the heat sink without insulating spacers in order not to decrease its thermal conductivity. Heat sink was isolated from the housing. The system itself includes automatic fans control as place for the elements on the PCB.
Power supply:
Power supply is slightly too powerful, so you can supply another, greater device with that. The transformer is patrially separated by a copper sheet (signal input is also separated).
Housing:
Housing is two cassette tape recorder Diora. Because of that housing, another kit AVT 2375 was added to the project. It was equipped with 5-points meter.
Cooling:
The device uses four isostats. Fans operate like that:
- activation of main fans (50% of their rotations). Fans are typical 12V PC fans connected in series
- activation of main fans (100%)
- activation of the small fans (50%)
- activation of the small fans (100%)
One of the advantages of IMHO is that before the heat sinks even get warm, they are already cool. In automatics, that threshold slides up to the thermal protection of the system. LEDs on the ventilation panel indicate their operation. You can backlight main fans as well.
Power supply is equipped with a control of its state. It consists of two LEDs indicating -41V and +41V of the power supply. Remember to paint black the edges of LEDs or divide them with a strip of film before pasting. Then the light is more selective after loss of one of the voltages.
Pictures:
Link to original thread - Wzmacniacz TDA 7294 Super Cooling