TDA7265 build doing my head in.

[Boscoe]

Basically i have built this amp 4 times now and used 2 different ICs using the schematic in the datasheet. I am doing a bridge design and using a +/-12V supply. All times all I get is a hum which is expected because of the unshielded cable I'm using to test it and no audio out into the speaker although one time I did get audio out although very quiet and noisy and if I turned it up too much I would get really heavy cracking noise too. So this time I now just have the hum and no audio out. I have checked over my work so many times now it's really annoying.

Can anyone help me?
Thanks
Boscoe.

[Andrew Eckhardt]

Basically at some point you have to admit that your circuit is not what is printed in the datasheet. Sometimes doing that as a first step helps a lot, makes it easier to find the difference. How about a close-up pic?

[Boscoe]

Originally Posted by Andrew Eckhardt

Basically at some point you have to admit that your circuit is not what is printed in the datasheet. Sometimes doing that as a first step helps a lot, makes it easier to find the difference. How about a close-up pic?

Here, this is really getting my nerves now!

[Boscoe]

Sorry about the bad qualtiy it was taken on an iphone!

[Andrew Eckhardt]

What is your circuit around pin 5? Also, what value are those local decoupling electrolytics? Can you get a shot of the bottom to show how you've routed the grounds?

[Andrew Eckhardt]

You know your vise is at -Vs right?

[Boscoe]

Originally Posted by Andrew Eckhardt

What is your circuit around pin 5? Also, what value are those local decoupling electrolytics? Can you get a shot of the bottom to show how you've routed the grounds?

The resistors around pin 5 are linking pin 10 and 2 and then 4 and 6.

Originally Posted by Andrew Eckhardt

You know your vise is at -Vs right?

I do yes. Nothing else electrical is attached to it.

[Andrew Eckhardt]

I meant what is the circuit connected to pin 5. What is the voltage on pin 5 to ground. Are your supplies actually +/- 12V?

All the grounds should be separate runs to nearly a single point.

The supply bypass caps could be closer, and the datasheet recommends having no less than 1000u/.1u right next to the chip.

[Boscoe]

Originally Posted by Andrew Eckhardt

I meant what is the circuit connected to pin 5. What is the voltage on pin 5 to ground. Are your supplies actually +/- 12V?

All the grounds should be separate runs to nearly a single point.

The supply bypass caps could be closer, and the datasheet doesn't give any recommendation about having less than 1000u/.1u right next to the chip.

My supply is exactly +/-11.5V.

All grounds run to pin 9 and then all other grounds like signal grd run to that.
I assumed that the 1000uF was for smoothing and as I was already using 4700uF I didn't think it would be necessary! I'll give that ago tomorrow.

Thanks

[Andrew Eckhardt]

The "application suggestion" table (have a good look-over) recommends the 1000u as a matter of stability, so should be local. Your 4700's are good where they are as ripple filters.

You do need to have less than +Vs - 6V on pin 5 to have the chip in run mode.