Earthquake tnt td5x

[imraneesa]

Hi all
This 5 channel amp came with two channels not working. It using TDA8920BJ IC each for two channels. I changed the IC now all 4 not working. Audio signals reaching the ic and there is oscillations on pin 1. This board totally have 3 494 ic. Anybody have any suggestions will be highly appreciated. Is there a way to force channels to play?

 

[Perry Babin]

What's the DC voltage on the MODE terminal?

Does the IC have ±rail voltage?

There may be 10 ohm resistors between the rail and Vdda/Vssa terminals of the IC. Confirm that they are not out of tolerance.

 

[imraneesa]

Dc voltage on mode is 0.1v.

Yes rails voltages present. Not seeing any 10ohms resistor.

 

[Perry Babin]

Check the voltage on the Vdda and Vssa terminals of both ICs.

 

[imraneesa]

The voltages are same as vddp and vssp i.e. 18v.

 

[Perry Babin]

You'll have to follow the circuit back from the mode pins to see what's driving it.

 

[imraneesa]

The trace went to one diode which is showing short. I removed it and the code on it is 5C. I am not getting any information about this 5C. What kind of diode is it.

 

[Perry Babin]

Photo?

 

[imraneesa]

Photo attached.

 

[Perry Babin]

I don't know the markings on MELF diodes. If no one here can help, post on the following forum:
https://www.diyaudio.com/forums/parts/

 

[imraneesa]

It is v633

 

[laluns]

I spoke to a guy here that use to do warranty work for earthquake in SA. He did not want to give me a diagram but has told me the values for the diodes

here you go and hope this helps:
1) V613 - 1N5041
2) V632,633, 634, 609 - 5V ZENER
3) V638, 639, 611, 612,629, 630, 631, DM1 & 2, D405, 404, 401, 402, 403, D541, 542, D551, 552, D902, 903,
D821, D811 - 1N4148
4) V616, 617, 1N4745A
5) D543, D553 - HER105
6) D901 - 1N4004
7) ZD11, ZD22 - 1N4753
8) D601, D602 - 1N5402
9) D121 - 1N4744
10) D881, 882, 883 - FR104

 

[imraneesa]

Thanks alot friend.

 

[laluns]

only a pleasure to help out