TDA7294 output stuck to -Vsupply

kroto · 12th February 2013, 09:03 AM

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?

regards,

pacificblue · 13th February 2013, 05:29 PM

If the input signal does not lead to that, then yes, the TDA is fried.

Mooly · 13th February 2013, 06:06 PM

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....

kroto · 14th February 2013, 04:58 AM

@pacificblue: no input signal, and no Coupling cap too.

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

thanks all.

Mooly · 14th February 2013, 06:47 AM

Without knowing the voltage rating I wouldn't use it anywhere that sees more than 16 volts across it.

JMFahey · 14th February 2013, 06:50 AM

Test it.

JMFahey · 14th February 2013, 12:56 PM

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.

Mooly · 14th February 2013, 04:26 PM

I'm thinking it could be like this,
MCBU5331K5 - MULTICOMP - CAPACITOR, 330PF, 50V | CPC

kroto · 18th February 2013, 07:25 AM

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.

daudinhbl · 21st February 2013, 04:36 PM

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-.

12th February 2013, 09:03 AM	#1
kroto diyAudio Member Join Date: Jun 2009 Location: Bandung	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? regards, __________________ _@ö sue

13th February 2013, 05:29 PM	#2
pacificblue diyAudio Member Join Date: May 2008	If the input signal does not lead to that, then yes, the TDA is fried. __________________ If you've always done it like that, then it's probably wrong. (Henry Ford)

13th February 2013, 06:06 PM	#3
Mooly diyAudio Moderator Join Date: Sep 2007	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.... __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

14th February 2013, 04:58 AM	#4
kroto diyAudio Member Join Date: Jun 2009 Location: Bandung	@pacificblue: no input signal, and no Coupling cap too. @mooly: that would be unsafe to be used as miller cap then. thanks all. __________________ _@ö sue

14th February 2013, 06:47 AM	#5
Mooly diyAudio Moderator Join Date: Sep 2007	Without knowing the voltage rating I wouldn't use it anywhere that sees more than 16 volts across it. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*


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14th February 2013, 06:50 AM	#6
JMFahey diyAudio Member Join Date: Mar 2009 Location: Buenos Aires - Argentina	Test it.

14th February 2013, 12:56 PM	#7
JMFahey diyAudio Member Join Date: Mar 2009 Location: Buenos Aires - Argentina	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.

14th February 2013, 04:26 PM	#8
Mooly diyAudio Moderator Join Date: Sep 2007	I'm thinking it could be like this, MCBU5331K5 - MULTICOMP - CAPACITOR, 330PF, 50V \| CPC __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

18th February 2013, 07:25 AM	#9
kroto diyAudio Member Join Date: Jun 2009 Location: Bandung	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. __________________ _@ö sue

21st February 2013, 04:36 PM	#10
daudinhbl diyAudio Member Join Date: Apr 2008	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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