My t-amp had been coming along nicely, that is until I tried to add a stiffener cap to the power supply. It was a 71v 10000uf cap from an old sony amp. So I wire it up in parallel, like this picture http://www.diyaudio.com/forums/attachment.php?s=&postid=878013&stamp=1143328719 turn it on and poof, the amp starts smokin. Also my right speaker starts to crackle and the woofer extended to the max.
Everything looked to be wired up correctly, but I took the stiffener cap out anyway, now I can't get any sound out of it. The led still lights up though. Is it toast? what about my speaker? Thanks.
Everything looked to be wired up correctly, but I took the stiffener cap out anyway, now I can't get any sound out of it. The led still lights up though. Is it toast? what about my speaker? Thanks.
jwb009 said:
Sorry to hear about that but it should be alright if you havent shorted anything. Check the connections again, you must have bridged the power into the outputs somewhere.
Did you connect directly to the pinof C10 that is closest to the chip? or did you just connect it to the board in the original position?
Lee
Member
Joined 2003
Since there is only 2 connections to the board with what you have done, the only thing I can think of is that you wired the red wire in your picture to the wrong side of the cap (C10). That would be, putting 12V on ground. However that shouldn't damage the amp as much as it would damage the power supply. Perhaps a photo would be helpful?
Once the magic smoke that makes all electronics work is let out, it is not likely that your amp will be functional.
Always, always measure your output before you connect it to your expensive speakers. For your speakers, first smell them to see if the voice coil has burned at all, then measure them with an ohm meter. You should be see the DCR of the speaker present on the meter. After everything looks good there, you are probably safe to hook them up to an amp and see if they make any noise.
Once the magic smoke that makes all electronics work is let out, it is not likely that your amp will be functional.
Always, always measure your output before you connect it to your expensive speakers. For your speakers, first smell them to see if the voice coil has burned at all, then measure them with an ohm meter. You should be see the DCR of the speaker present on the meter. After everything looks good there, you are probably safe to hook them up to an amp and see if they make any noise.
Probe around and check for the proper voltages at certain pins with your speakers disconnected.
Pins 4,9: 5V
Pins 11,15: 2.4-2.5V
Pin 36: about 10V above the supply voltage
Did both speakers push out the last time you turned the amp on? Was there a lot of smoke or a little bit of smoke when something fried? Check the output diodes to make sure it wasn't one of them that went (probably not). Chances are you fried the internal output mosfets and they're shorting the output to the supply rail. If that's the case you'd need to replace the chip.
Pins 4,9: 5V
Pins 11,15: 2.4-2.5V
Pin 36: about 10V above the supply voltage
Did both speakers push out the last time you turned the amp on? Was there a lot of smoke or a little bit of smoke when something fried? Check the output diodes to make sure it wasn't one of them that went (probably not). Chances are you fried the internal output mosfets and they're shorting the output to the supply rail. If that's the case you'd need to replace the chip.
are you certain the
cap was good to begin with and not internally shorted ?
was the cap totally discharged before wiring it in ?
i just built a psu and had a cap with a slight dent in it so i measured it and sure enough it was shorted.
and ive built powersupplies before where if a cap had a stored charge of lets say 10v that charge would just get added to the supply voltage when it got powered on.
cap was good to begin with and not internally shorted ?
was the cap totally discharged before wiring it in ?
i just built a psu and had a cap with a slight dent in it so i measured it and sure enough it was shorted.
and ive built powersupplies before where if a cap had a stored charge of lets say 10v that charge would just get added to the supply voltage when it got powered on.
BWRX said:
I checked these voltages, everything was good except the pin 36 voltage, that is measuring 13.2v (unless i measured the wrong pin). Only the right speaker would get extended when turning it on, but now it isn't even doing that anymore. I'm thinkin it's fried, but hey, it gives me an excuse to get an amp6
The channel went bad because C10 is the wrong cap. I just looked at the only SI I have left and saw what C10 is connected to. That is part of the output filter for the right channel. You did fry something in the output stage on the chip (the smoke you saw) because you connected the supply to the output of the amp. You want to to put the large filter cap in parallel with either C11 or C12 - NOT C10.
Lostcause said:
Hey whaddya know! Sorry about the mixup. What's the designator for the 0805 ceramic cap on the other side of the board that's part of the output filter? (It's right next to C9 and looks like it's labeled C10). I couldn't see the real C10 because the cap is covering the label on the board I have
(it's one of the first ones that SI produced).jwb009 said:
If you said you aren't seeing 10 volts above the supply rail on pin 36 then the output stage will not work properly. It supplies the gate drive for the high side mosfets on the chip.
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