Part-1
Before proceed to repair, note whether the sound mute function is On. If ON, make it OFF. If this setting is alright, check the voice coil of the speaker with a multimeter. If speaker also has found good then proceed.
Contd:-
Before proceed to repair, note whether the sound mute function is On. If ON, make it OFF. If this setting is alright, check the voice coil of the speaker with a multimeter. If speaker also has found good then proceed.
- Check all the solder terminals [9 of them] of the audio output IC (IC251_ TDA 2007). It is best to resolder all these solder terminals of thie IC, by applying a little more solder, becuse some loose solder points are very difficult to detect, as they might be microscopic to normal vision.
- If all of above are found OK, check the supply voltage comes to this IC. Its main supply voltage is given to its pin (8). 14VDC should be present at this pin. This voltages comes from SMPS power supply section, through a resistor [protection resistor]. [R613 - One Ohm]. Check this resistor for continuity. If found open, make sure that there is some short circuit with the circuit related to audio output section.
- Check (C251 - 1000Mfd 25V) for short. It is best to measure the voltage between pin number (8) of the audio output IC to main ground. In most cases, if the measure resistance is very low; say lower than 15Ohms or so, the audio output IC is likely to be shorted. Resolder out the audio ouput IC from circuit, and measure this resistance. Still found low, repalce [C251-100MFD 25V). It is shorted.
- If the voltage at pin (8) of audio output is found OK, and thee is no output from the speaker, check the voltage at pin (9) [audio output]. It should be about 6.8VDC. If this voltage is found abnormal [approximately equal to the supply voltage - 14VDC of found to be zero volt]; Without any doubt, repalce the audio output IC. It has damaged.
Contd:-
