TDA7294 output stuck to -Vsupply - diyAudio
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Old 12th February 2013, 09:03 AM   #1
kroto is offline kroto  Indonesia
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Question TDA7294 output stuck to -Vsupply

one of my (the farthest from the fan) TDA7294 output stuck to -Vs, why was that?
is it dead? does anyone have the same experience?

the heatsink is pretty small but with a fan, and box ventilation is rather small.
VS +/-30Vdc.


and what is the voltage rating of general brown ceramic disc cap, such as this pic?
Click the image to open in full size.

regards,
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Old 13th February 2013, 05:29 PM   #2
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If the input signal does not lead to that, then yes, the TDA is fried.
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Old 13th February 2013, 06:06 PM   #3
Mooly is offline Mooly  United Kingdom
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The cap is an unknown voltage wise. It could be as low as 16Vdc, more probably 50Vdc but as we don't know for sure....
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Old 14th February 2013, 04:58 AM   #4
kroto is offline kroto  Indonesia
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@pacificblue: no input signal, and no Coupling cap too.

@mooly: that would be unsafe to be used as miller cap then.

thanks all.
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Old 14th February 2013, 06:47 AM   #5
Mooly is offline Mooly  United Kingdom
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Without knowing the voltage rating I wouldn't use it anywhere that sees more than 16 volts across it.
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Old 14th February 2013, 06:50 AM   #6
JMFahey is offline JMFahey  Argentina
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Test it.
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Old 14th February 2013, 12:56 PM   #7
JMFahey is offline JMFahey  Argentina
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Not forgetting that small value ceramic caps auch as this one, are usually rated for 500V or even 1 KV.
Never ever saw a 16V rated ceramic , althouh in the highest values (such as 0.1uF ) I have used some 25V rated ones.
You do what you want, but personally *I* would use it and not worry a second.
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Old 14th February 2013, 04:26 PM   #8
Mooly is offline Mooly  United Kingdom
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I'm thinking it could be like this,
MCBU5331K5 - MULTICOMP - CAPACITOR, 330PF, 50V | CPC
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Old 18th February 2013, 07:25 AM   #9
kroto is offline kroto  Indonesia
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i have been use such ceramic (100pF) for miller at supply 35V with no failure though.

just curious since some friend say most of it rated at 50v and not blow.
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Old 21st February 2013, 04:36 PM   #10
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Check R 22K from pin 14 (OutPut) to pin 2 (NFB). If you don't connect R feed back, the Voltage at pin output will set to V-.
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