prolem chipamp TDA7294

[vthieu]

Hi !every body
I first DIY Chipamp with this application schema TDA7294,but the output in pin 14 have 4Vdc. It make the sound very bad . I change 2 chip TDA but nothing . Any one have ideal help me please!
Because I hear TDA7294 very easy to make with some little component and very easy suscessful. Hu hu

An externally hosted image should be here but it was not working when we last tested it.

 

[tiltedhalo]

DC offset

Are your values all the same as the schematic? are you using the 22K NFB resistor and is the value the same as the input shunt resistor? a difference between the two can result in an offset. Did you include the boot strap if so try a different value cap. Also try raising the value from 680 to 1K for the NFB to ground resistor.

 

[ashok]

Check your circuit again . Take a break and look at it after a couple of days. Sometimes you overlook obvious mistakes if you keep spending too much time on it.

The application circuit works very well.
Search for 'TDA7294' on this forum. You will find lots of informatioin and 'warnings'.

 

[vthieu]

http://www.flickr.com/photos/15683789@N00/2212069488/
I try replace R1 22K link pin 3 (in+) , but no nothing ,I meter pin 14 still -4Vdc ,What can I do ?

 

[vthieu]

Many thank for your ideal !
I will check it again on another day , when I refesh!But I no found mistake in PCB with little component , what can I do ?
R (in+) pin 3 =22k
R (in-)=680
R link speaker- (in-) = 22K

 

[m-tech]

Check polarity of C2 and C5.

 

[ashok]

Remove C2 and C5 . Leave the terminal open ( do not short the terminals ). If the problem goes away then you had a wrongly connected capacitor.
I suspect wrong polarity in C5 but I could be wrong.
If you still have a problem, check the supply pins for proper voltage . What voltages are you using in the power supply?

C3 and C4 are connected with -Ve terminal to ground ?

 

[vthieu]

C5 : + link spker
- link pin6
C2 : + link pin2
- link GND
Please tell me if I change C5 = 47uF or 100uF what happen?
it still wrong , 4Vdc in pin14?
Vs- = -28 Vdc
Vs+ = +28Vdc
C6&C8 cap for Supply . I think if i wrong conect polary cap -> BUM BUM.But it OK ,I think ghost could be in my PCB.

 

[czbass]

I've destroied many TDA7294s by mistake..

I'll use a LM3886 to make a new amp.

 

[Fossil]

check all pins connected to ground, eg, Pin 1 & 4...solder again.