Hi folks ,
Its a subwoofer box with 4 channels by 2 TDA8920BTH Ic .
Please help in tracking the fault, one of the ic have no sound output, i swapped the ic and still no sound this make sure that ic is working. Also power lines and mode pin is shared and R531 and R532 are not blown. So the fault must be at output stage which i really think but i dont know how to track, i tried to unsolder both inductor L501 and L502 one by one to make sure if downstream error but still none of the two channels from this ic is playing any sound. Any suggestions

 

You swapped IC501 and IC502.
Did this confirm that both ICs are working?

 

You swapped IC501 and IC502.
Did this confirm that both ICs are working?

Yess after swapping its confirmed both are working. So there is fault in the other part of circuit

 

What you need now is an oscilloscope or an audio probe.
You can make your own audio probe with a powered PC speaker. Use a 10 μF capacitor as your probe and feed the signal into one channel of the amplified speaker. Ask if you do not know how to do this.

 

Alright yes i have created it . The probe that goes in pc speaker in with capacitor connected on L/R side. Now ? Do i have to plug in the source and put the probe on input track ??

Also i tried to touch the input points with bare finger and on working ic it did make the humm sound but on non working its not producing any sound.

 

Do i have to plug in the source and put the probe on input track ??

Yes, but would suggest the outputs of IC401D and 401C at the junction of C417/ R501 and C418/ R502 for starters.

 

Yes, you need an input signal.
Probe all four outputs of IC401 and compare all four channels.

 

Update :

I have done the probe test and yup it's getting proper input at all 4 channels. Although at one point its sounding more bassy must be because its subwoofer channel. But it does getting the audio without any additional noise.

Next step ??

 

Move along the signal chain.
Test at C510, C511, C514, C515.

 

You mentioned no audio on pin 1 of the IC.
But you didn’t identify which IC you’re talking about.
SGIOTO mentioned IC401 C and D, but there is no pin 1 there.

 

I think i fried the ic now while testing it . It showing 27 volts on speaker terminal