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Soundstream DaVinci help needed
Soundstream DaVinci help needed
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Old 21st August 2017, 04:42 PM   #1
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
Default Soundstream DaVinci help needed

Hey folks, I could really use some help here. I've been working on this blown DaVinci for about a day now, I'm not having much luck. I repaired the channel 7 (subwoofer channel) power supply when I first got it. I thought u had it fixed, but when I got it back together it wouldn't work. I put it on the back burner for quite some time and just started working on it again.

The amp draws about 15a at idle, the channel 7 supply is not producing any voltage and at least initially the 4 fets for the channel 7 supply would quickly overheat. I pulled and checked fet gate drivers, they are fine, fets, and hate resistors check ok too. I have good drive from the sg3524 without the b+ connected. If I pull the rectifiers from this supply it fires up and runs. I pulled all the outputs on that channel, they are fine. Pulled the drivers, they test good, pulled the pre-driver board and the supply will won't come up. I also pulled the voltage regulators and the rail caps, still won't work.

I obviously skipped a step in that I haven't yet checked the feedback or shutdown on the sg3524. I'll do that at after I feed the kids lunch. It appears the pwm controller does keep producing pulses though when b+ is connected. I have been leary about leaving it powered long enough to do much testing.

Does anyone have any other ideas? BTW, this is a revision a model with all the design patches all over. Makes it even tougher to sort out what is going on.

Thanks,
Jason

Last edited by jacampb2; 21st August 2017 at 05:41 PM.
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Old 21st August 2017, 05:43 PM   #2
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
Shutdown pin is low, Pin 2 is at 2.5V, Pin 1 is at or close to ground.

I just rechecked the fets in channel 7 PS, they are still good. At this point I am thinking I may have a shorted inductor. I'm going to pull it and "ring" it, see if I'm going to need to rewind it.
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Old 21st August 2017, 06:19 PM   #3
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
Ok, now I am almost out of ideas. I pulled the inductor for the PS in question, and just decided to check if the PS would come up and produce the rails with the inductor out of the equation. It still pulls way to much current and no DC after the rectifiers. I am really stumped on this. There is literally nothing left in circuit after the rectifiers now.

I think I am going to pull the rectifiers again. I don't know what else to try. Is it possible for the transformer to produce AC with a shorted winding and only fault when the rectifiers are in circuit? One winding on this transformer does look like it has gotten warm...

If anyone has any thoughts, please share. I hate being stumped like this.

Thanks,
Jason
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Old 21st August 2017, 06:32 PM   #4
Perry Babin is offline Perry Babin  United States
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Location: Louisiana
Does the current draw change when you twist/push/pull the transformer?
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Old 21st August 2017, 06:46 PM   #5
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
No, current draw does not change.

I just removed the rectifiers again, attached below is the waveforms on the secondary of the transformer, referenced to secondary ground. I thought maybe they weren't 180 out of phase, or some other oddity, but the AC output looks really good to me.

I'll check the rectifiers again. I wonder if there is a slightly leaky diode in the bunch...

Thanks,
Jason
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Old 21st August 2017, 06:48 PM   #6
Perry Babin is offline Perry Babin  United States
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What's the deadtime look like on the FET gates?
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Old 21st August 2017, 06:51 PM   #7
jacampb2 is offline jacampb2  United States
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Location: Beaverton, Mi 48612
I will check, but I might have found it. One half of one of the rectifiers leaks current, I'm going to reinstall just two good and see if it powers up
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Old 21st August 2017, 06:59 PM   #8
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
Good lord, I feel like a idiot! That was it. I have no idea how I missed it when I checked them yesterday, but I have half of the parts pulled from this damn amp now. I guess it's a lesson to double check the obvious.

I'll get it back together and keep you all posted on if she works. Thank you!
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