Hy
My TDA7250 based amp went on "fire" today. The problem is that i do not know what's toasted. The 7250 or the TIP142/147.
How can il tell what's fried ?
Thanks
P.S. I want to replace the 142/47 tip's with TIP 36C and 35C. Does anyone knows how they sound ? However they have maximal ratings higher than 142/147.
My TDA7250 based amp went on "fire" today. The problem is that i do not know what's toasted. The 7250 or the TIP142/147.
How can il tell what's fried ?
Thanks
P.S. I want to replace the 142/47 tip's with TIP 36C and 35C. Does anyone knows how they sound ? However they have maximal ratings higher than 142/147.
Ford_V6 said:
First thing to do is try to find out why it toasted.
Now, measuring a bad transistor is much easier than measuring a bad IC. Hope you know how to measure transistors. In case you don't know, here's a link:
http://www.eatel.net/~amptech/elecdisc/trnsistr.htm
If you feel things are really toasted, I wouldn’t hesitate and replace the 7250 as well.
TIP142/47 are darlingtons, TIP36/35 are normal transistors.
You can't just switch them.
/Hugo
The amp was running without the speakers connected when toasted. Is this the reason ?
I have read in another thread that this amp requires a 100 nf cap. between the + an - right next to the ic.
Now i will add this capacitor too.
I still don't know why the amp is shutting down at high volume.
When the amp toasted R17 and R19 toasted too.
I have attached the link to schematic after wich the amp is built.
http://home.eunet.cz/rysanek/tda7250.gif
I have read in another thread that this amp requires a 100 nf cap. between the + an - right next to the ic.
Now i will add this capacitor too.
I still don't know why the amp is shutting down at high volume.
When the amp toasted R17 and R19 toasted too.
I have attached the link to schematic after wich the amp is built.
http://home.eunet.cz/rysanek/tda7250.gif
Probably not.Ford_V6 said:
If you mean pin 4 and 14, they are required.
Did he play? What do you mean with shutting down? There is an overload current protection build in the 7250. Could be that.
Can't see R17/19. BTW, wich voltage do you apply on the +/- Us?
And, are your transistors broken?
/Hugo - needs a schematic with part names.
I apply +/- 38 V
When i raise the volume the amp stops playing.
When i lower the volume the amp starts playing again.
When the amp toasted it was running only with one speaker conected. The TIP's are toasted too. ( C and E pins are in short circuit )
The amp played a few days.
The 100 nf cap. is not on the schematic. it has to be installed on pin 4 and 14 ?
Thanks for helping me out here
I have atached the schematic with part numbers.
When i raise the volume the amp stops playing.
When i lower the volume the amp starts playing again.
When the amp toasted it was running only with one speaker conected. The TIP's are toasted too. ( C and E pins are in short circuit )
The amp played a few days.
The 100 nf cap. is not on the schematic. it has to be installed on pin 4 and 14 ?
Thanks for helping me out here
I have atached the schematic with part numbers.
Ford_V6 said:
Depends how loud you go. If you raise the volume towards the limit of the amp, it will mute. (protection) If the amp mutes at low volume, it is likely the 7250 is broken or other broken parts are causing the mute.
First replace all bad components. Remember there's a major difference in schematic, using transistors vs. darlingtons. Look at the datasheet and study it:
http://us.st.com/stonline/books/pdf/docs/1472.pdf
Forget the 100nF for the moment.
/Hugo
How do you check the chip?
Check the output pins for DC volts. If you have the rail voltage, chances are that your chip is blown. I'd replace it anyway.
That is very weird topology to me. I don't see that ever in my line of work. I only see collector resistors on a quasi complimentary amp. All others use emitter resistors.
Good luck with the amp though!
Chris
Check the output pins for DC volts. If you have the rail voltage, chances are that your chip is blown. I'd replace it anyway.
That is very weird topology to me. I don't see that ever in my line of work. I only see collector resistors on a quasi complimentary amp. All others use emitter resistors.
Good luck with the amp though!
Chris
Salut Ford V_6 ,
Este vorba de un modul de putere cumparat de la Adelaida - Craiova , bazat pe TDA7250 ?
Daca da , sa stii ca au vicii de proiectare iar tranzistoarele nu rezista in sarcina la mai mult de 60 - 70Wrms in sarcina.
Toate aceste module au aceasta problema privind deconectarea la suprasarcina. Se mai poate ridica pragul de MUTE , dar , in orice caz nu merita efortul .
Daca totusi vrei sa experimentezi , incearca MJ11015/11016.
Eu am reusit sa ajung la 180W rms la +/- 48v masurat la 1% THD.
Oricum efortul nu a meritat banii si timpul pierdut.
Exista alte scheme incomparabil mai bune .
Salut !
Este vorba de un modul de putere cumparat de la Adelaida - Craiova , bazat pe TDA7250 ?
Daca da , sa stii ca au vicii de proiectare iar tranzistoarele nu rezista in sarcina la mai mult de 60 - 70Wrms in sarcina.
Toate aceste module au aceasta problema privind deconectarea la suprasarcina. Se mai poate ridica pragul de MUTE , dar , in orice caz nu merita efortul .
Daca totusi vrei sa experimentezi , incearca MJ11015/11016.
Eu am reusit sa ajung la 180W rms la +/- 48v masurat la 1% THD.
Oricum efortul nu a meritat banii si timpul pierdut.
Exista alte scheme incomparabil mai bune .
Salut !
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