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Class D Switching Power Amplifiers and Power D/A conversion

No sound from TDA7492P Amp
No sound from TDA7492P Amp
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Old 16th January 2018, 09:13 AM   #1
dutchronnie is offline dutchronnie
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Default No sound from TDA7492P Amp

I made a bluetooth speaker with the TDA7492P red amplifier board.
But since yesterdag i have no sound anymore from the board.

I think i made a short between the speaker connections.
Can somebody tell if this short destroys the board?
And if it will only a componenent which one can it be, so i can replace the component.

bluetooth is stil working, and also the power led.
Hope someone can help
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Old 16th January 2018, 02:49 PM   #2
FauxFrench is offline FauxFrench  France
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The short circuit may have destroyed the TDA7492 chip. Perhaps not the current itself (there is probably an over current protection) but voltage spikes generated by the filter coils.

First the 10 Ohm test: No power supply or input signal. With an Ohm-meter in the 20K range. Looking at the two power terminals ("+" and "-") and the four speaker output terminals. If you measure between any (two) of these six terminals, do you get an Ohm-meter reading of less than 10 Ohm?

IF you have a combination with less than 10 Ohm, the chip is very likely defect, if not, it may still be defect.

If both channels are dead, it is not likely to be any other component than the TDA7492 because any other component would affect only one of the two stereo channels.
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Old 16th January 2018, 08:27 PM   #3
dutchronnie is offline dutchronnie
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I have measured the resistance between the + and - of the left speaker terminal and i get a reading of 0.394 MOhm, the same value on the right channel.

Both of the channels are death.
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Old 16th January 2018, 08:49 PM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by dutchronnie View Post
I have measured the resistance between the + and - of the left speaker terminal and i get a reading of 0.394 MOhm, the same value on the right channel.

Both of the channels are death.
The easiest fix is a new pcb.
The TDA7294 are a pig to unsolder and replace unless holes are large.
You can cut all the pins high up then de-solder them holding the top of the pin with long nose pliers gently pull on pin while heating with iron.
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Old 17th January 2018, 11:19 AM   #5
dutchronnie is offline dutchronnie
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I have ordered a new PCB, but it takes 3 weeks before it arrives from China.
I can not replace the chip, it is all sms components
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Old 17th January 2018, 12:04 PM   #6
FauxFrench is offline FauxFrench  France
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None of the output terminals have less than 10 Ohm to supply "+" or "-"?

Next step is the use of an oscilloscope and check the signal on each pin of the TDA7492. If it is not to learn about the TDA7492, it is easier just to buy another board.

It is possible to replace a TDA7492 chip (even SMD) if you are experienced with soldering. But, you need to get another chip and a new board is not that much more expensive.
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Old 31st January 2018, 04:38 PM   #7
dutchronnie is offline dutchronnie
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Today i received a new board from china.

After i connected the speakers to the board. i smell something terrible. a saw smoke from the speaker.

Ohno not again.

It is the right channel that is wrong.
I measure a voltage of 12V on the right channel.
the left channel is only 0.03 volt
who knows what is wrong and how can i fix this?
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Old 31st January 2018, 04:40 PM   #8
nigelwright7557 is offline nigelwright7557  United Kingdom
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Are you connecting a new amplifier to a bad speaker ?
If you are it will just blow up the new amplifier.
What supply voltage are you using ?
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Old 31st January 2018, 04:46 PM   #9
tauro0221 is offline tauro0221  United States
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Hi,
You did not say if the speaker was disconnected when you check the chip output pin resistance. Did you check the speaker resistance? Maybe you have a shorted speaker coil.
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Old 31st January 2018, 04:51 PM   #10
dutchronnie is offline dutchronnie
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The speakers were alright.
I measure the voltage with no speakers connected.

It must be something on the board
When i connected the right channel there was sound but after a while it begun to smike and smell, now the speaker is blown up.
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