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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 31st January 2018, 04:57 PM   #11
dutchronnie is offline dutchronnie
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I measured the voltage again.

When there is no bluetooth connection is measure on both channels 0.01 volt
with buetooth connection and music playing i measure on the left channel 0.03 volt
and on the right channel 19 volt

my power source is 19 volt.

I tried several times to switch on and off the bluetooth connection, and everytime when i have connectione there is 19 volt on the right channel.

I also measure the resistance between the + power connector and the + speaker connector.
with bluetooth off there is no resistance (open loop)
and with bluetooth on there is resistance (closed loop)

does somebody know what the problem may be?
and is there somewhere a schematic of this board?

Last edited by dutchronnie; 31st January 2018 at 05:15 PM.
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Old 31st January 2018, 05:25 PM   #12
nigelwright7557 is offline nigelwright7557  United Kingdom
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Do you have coupling capacitors on the input to the amp ?
If not there could be DC out of the Bluetooth module being amplified.
Try putting a 0.1uf capacitor between Bluetooth audio out and amplifier audio in.
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Old 31st January 2018, 05:35 PM   #13
dutchronnie is offline dutchronnie
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I don't know where i can find the bluetooth audio out and amplifier in on the board.
But it is a standard board, i should be working.

I have now two board this board is exect the same as the other one, and that one was working wel, til i made a short.

I have tried the board also with a 12v power supply, and then there is only 4v on the speaker out.

I also tested the bluetooth again, but it looks like there is only an high voltage when the music is playing, and not when there is a bluetooth connection

Last edited by dutchronnie; 31st January 2018 at 05:42 PM.
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Old 31st January 2018, 05:47 PM   #14
dutchronnie is offline dutchronnie
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http://www.diyaudio.com/forums/attac...3-2_1_1600-jpg


this is a photo of the board
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Old 31st January 2018, 06:05 PM   #15
nenad88 is offline nenad88
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Does it works with bluetooth? here is one video with similiar problem YouTube
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Old 31st January 2018, 06:09 PM   #16
bullittstang is offline bullittstang  United States
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Might really help if you attached a clear picture of exactly how you have it hooked up. Connections labeled clearly.

Hard to believe both have the same issue, when you said the first one was working fine (for how long?) before you shorted something?
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Old 31st January 2018, 06:50 PM   #17
dutchronnie is offline dutchronnie
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No, both boards didn't have the same issue.

The first board i made a mistake, i shortend the speaker outputs. after that the board didn't work anymore.

I ordered a new board, it arrived today. I hooked up the speakers black wire on the - red wire on the +
made bluetooth connection, the right speaker begun to smake and smell terrible.
That is what happend and nothing more.

The youtube video is not the problem i have.
I have a big voltage on the right channel when playing music, which cause to blow up the right speaker.

Last edited by dutchronnie; 31st January 2018 at 06:55 PM.
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Old 31st January 2018, 07:15 PM   #18
FauxFrench is offline FauxFrench  France
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You are not lucky with your boards.
My experience is that even a short lasting short-circuit of the output pins may damage the class D chip permanently. Therefore, try to make your last purchase work for a start.

The TDA7492 is supposed to work down to 8V so use a 12V supply until it seems to work. There is no need to provide more energy to destroy your amplifier as long as the amplifier appears to be defect.

Connect two 8Ohm dummy loads to the outputs, connect your 12V supply to the DC-plug and turn the power on:
Do all four 330uF/35V decoupling capacitors have 12V across them?
Without any Bluetooth connection, what is the DC voltage measured across each of the two dummy loads?
Do the DC output voltages across the two dummy loads change when you connect to the Bluetooth receiver and starts playing music?

NB: NEVER use your good speakers for a start when you test a new amplifier. In case of doubt, use dummy resistors. In case of confidence, use some cheap test speakers until you are sure that the amplifier works correctly.
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Old 31st January 2018, 07:19 PM   #19
dutchronnie is offline dutchronnie
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I found a schematic of the board, not exactly the same but it looks like the outputs are the same

I have 19 volt on ic1 between pins 2,3 and 8,9

How is this possible?, is it a wrong ic ?
Attached Images
File Type: png schema tda.PNG (116.5 KB, 47 views)
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Old 31st January 2018, 07:34 PM   #20
dutchronnie is offline dutchronnie
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i put on each channel a 8 ohm resistor
And attached a 12v power supply

all four capacitors do have 12v across them.
i measure on the right channel 0.007 volt and the left 0.017 volt
when bluetooth connects i didn't have time to measure but is looks like it is more than 6 volt on the right channel, the risistor begins immidiatly to burn

Quote:
Quote:
NB: NEVER use your good speakers for a start when you test a new amplifier. In case of doubt, use dummy resistors. In case of confidence, use some cheap test speakers until you are sure that the amplifier works correctly.
I know it was stupid
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