TDA1554 problem

[baskar007]

Hi guys,
I build an amp using TDA1554 chip.
i was checked all connection it's ok. but the problem is, When i give a power supply to the circuit it's getting hot within few seconds(5 sec or less), Even no input signal,no load (speakers not connected)

I think this problem caused by the circuit is wrong value of parts or missing basic methods!
Here is circuit design i used:

**broken link removed**

i changed the input capacitor 220ηF to 10µF.
4, 15, 9 pins are not connected to any.
power supply is 1N5408 diodes(4),1000µF capacitor with 12V 3amp transformer.

 

[Nigel Goodwin]

What's the maximum voltage rating of the chip?, and have you measured the actual voltage you're feeding it - a 12V transformer will give something like 18V on the chip.

Otherwise it's probably oscillating, layout is often critical on these audio chips, have you followed the recommended PCB layout?.

 

[solis365]

try putting a fairly large capacitor to ground from pin 4, the supply voltage ripple rejection. something like 100uf or 470uf

other than that check your connections, are you within the supply voltage ranges?

can you measure the output with a scope? that will tell you if its oscillating.

 

[baskar007]

I have checked the transformer output voltage its 12.3 volt, and chip's range between 12v to 18 volt.

i am using Stripboard. all connection are done with small copper wire used(i dont know it's size but basically it's used for transformer primary coil)

 

[Nigel Goodwin]

I have checked the transformer output voltage its 12.3 volt, and chip's range between 12v to 18 volt.

The transformers output isn't really very important as such, it's the DC on the chip that matters - and a 12V transformer is going to be pushing the top limit for the chip.

i am using Stripboard. all connection are done with small copper wire used(i dont know it's size but basically it's used for transformer primary coil)

It may well be unstable then?, do you have access to a scope so you can check?.

 

[baskar007]

I have no scope
any other idea?

 

[Nigel Goodwin]

I have no scope
any other idea?

Post a picture of how you've built it.

Also, check what DC voltage is actually on the chip.

 

[baskar007]

I attached photos.
But its does not clear because i taken from vga cam. my bad luck my cam is not there (in my house). sorry.

and the circuit is same as above picture

thanks for taking care for me. rep added

 

[Nigel Goodwin]

Well the pictures are pretty small and blurred, but the circuit is spread out over a large area, and components are even spaced off the board on long wires.

These are all very bad ways to build such a circuit, and very likely to make it oscillate.

 

[baskar007]

is these will make the circuit oscillate?
Ok i will build it on new board with neat .

and then i'll reply thanks sir.

 

[audioguru]

The audio amplifier IC circuit made in a mess will oscillate.

 

[baskar007]

Now i rebuild the amp. now also it gets hot even no input and loads.

I was tried with a input signal and loads,it gives noise like humming with a sound but very low sound!.

 

[Nigel Goodwin]

You may have killed the chip previously, but also it depends on how good your new layout is - try and post decent quality pictures of both sides of the board.

 

[transistor495]

It is reverse polarity safe so I think you've shorted pins somehow. Might have fried already. You should clean the board well for removing the solder dusts before switching on.

 

[baskar007]

I double sure i never make short circuit on this circuit, Because i always check circuit twice time before giving power. Is there is any ways to find my ic is fried or not?

in my area buying this ic is does not easy. so please help me guys.

 

[solis365]

If the chip has thermal and short circuit protection (which it does, according to the datasheet) then it seems the only way to fry it is too much supply voltage or a gigantic input signal.

Really, the best way is to find someone with an oscilloscope you can borrow to see if it is oscillating, check the level of your inputs, and perhaps your power supply quality (does it have a high ripple?)

Since your transformer is close to the maximum supply voltage, try building a regulated power supply. So transformer, rectifier, filter capacitor, and then a regulator IC and some more filtering. If you have a double-ended supply (i.e., +/- 12V) you will need a negative regulator IC as well. Both regulators should be adequately heatsinked and capable of supplying enough current. Design the regulator circuits to give you a DC voltage within the operating range of the amplifier (the datasheet will tell you how to set the regulator's voltage), and check this DC voltage before you connect to your amp.

However this is a complicated solution which could potentially introduce more problems that will be hard to solve without a scope. Do you have access to a regulated lab power supply? You can use that to test.

 

[Nigel Goodwin]

I double sure i never make short circuit on this circuit, Because i always check circuit twice time before giving power. Is there is any ways to find my ic is fried or not?

in my area buying this ic is does not easy. so please help me guys.

We've already told you that layout is critical, post the new layout, bottom side as well.

 

[baskar007]

thanks friends