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Old 29th March 2006, 09:28 PM   #1
jwb009 is offline jwb009  United States
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Default T-amp up in smoke

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/attac...amp=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.
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Old 29th March 2006, 10:14 PM   #2
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Default Re: T-amp up in smoke

Quote:
Originally posted by jwb009
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/attac...amp=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.
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?

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Old 29th March 2006, 10:30 PM   #3
jwb009 is offline jwb009  United States
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I connected just like the picture, using a little jumper from c10 to the (+ive). Everything is now wired up like I had it before, but still nothing. No 'thump' either when turning it on.
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Old 29th March 2006, 10:38 PM   #4
DcibeL is offline DcibeL  Canada
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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.
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Old 29th March 2006, 10:41 PM   #5
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Quote:
Originally posted by jwb009
I connected just like the picture, using a little jumper from c10 to the (+ive).

Hmmm, well it was meant to be either/or on the connection but you have effectively just bypassed the on/off switch....always on!
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Old 29th March 2006, 10:45 PM   #6
jwb009 is offline jwb009  United States
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Well, the speaker seems to work fine, I have it hooked up to my promedia amp and it's workin. But when I try it on the t-amp as soon as I turn it on, I now get the thump, and the 5.25" woofer gets extended to the max and stays that way. hmmm
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Old 29th March 2006, 10:48 PM   #7
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Quote:
Originally posted by jwb009
Well, the speaker seems to work fine, I have it hooked up to my promedia amp and it's workin. But when I try it on the t-amp as soon as I turn it on, I now get the thump, and the 5.25" woofer gets extended to the max and stays that way. hmmm

Pictures......

What exactly smoked?

What other mods have you done?
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Old 29th March 2006, 10:58 PM   #8
BWRX is offline BWRX  United States
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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.
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Old 29th March 2006, 11:21 PM   #9
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Quote:
Originally posted by jwb009
the 5.25" woofer gets extended to the max and stays that way. hmmm
If you care about your speakers, get some sort of a dummy load for testing a new or modified amp. A high wattage 8R resistor works fine and will allow you to measure the DC offset.
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Old 30th March 2006, 01:11 AM   #10
snkby is offline snkby  United States
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Default 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.
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