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Class D Switching Power Amplifiers and Power D/A conversion

TPA3116 Disaster - Boom
TPA3116 Disaster - Boom
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Old 15th May 2018, 07:37 PM   #1
rollingreenhills is offline rollingreenhills
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Smile TPA3116 Disaster - Boom

Hello, New here.

I was wondering if someone could educate me on what happened today:

I have a 20 year old amplifier that stopped working, I opened it up and found that the power supply was still humming away, and producing a variety of voltages (AC).

On the board of the defunct amplifier were 2 x 200v. 6a bridge rectifiers which I thought I could use to connect to the AC out and get back to DC. I wired these straight to the AC output and verified with a multi meter that they were putting out:

-12V for bluetooth panel
-20V for TPA 3116 (2 x 100W) x 2 - wired in parallel to supply

The blue tooth panel was wired in first and worked fine. I then wired up the amplifier, turned them on (no load) and plugged in. . . . . . . and was treated to a small firework display. Smoke and cracking from all over the place. Both Amplifiers and Bluetooth panel were dead.

What happened here? I checked the voltage all was well. . . .

My only thought is that I overloaded the bridge rectifier causing it to fail? But I have a TPA3116 2.1 board (200W) that draws 50W MAX when playing drum and bass, so I was not expecting a big draw on current.

So I've had the failure. Now I need a teacher. . . .will you be my Yoda?
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Old 15th May 2018, 09:08 PM   #2
Khron is offline Khron  Finland
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Class-D amplifiers rarely (if ever) like working without a load connected, so there's that...
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Old 15th May 2018, 09:14 PM   #3
jean-paul is offline jean-paul  Netherlands
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Pictures, schematics and any info available help tremendously in finding answers also when Yoda is involved.

“Do. Or do not. There is no try.” Yoda, The Empire Strikes Back.

Some words have red LEDs blinking...

Quote:
Originally Posted by rollingreenhills View Post
On the board of the defunct amplifier were 2 x 200v. 6a bridge rectifiers which I thought I could use to connect to the AC out and get back to DC ??. I wired these straight to the AC output and verified with a multi meter that they were putting out:

-12V for bluetooth panel
-20V for TPA 3116 (2 x 100W) x 2 - wired in parallel to supply
What do you mean with "AC output" ? I sure hope you did not feed the amps AC as they are allergic to that.

Tip: always use AC or DC when voltages are mentioned (or use + or - when it is DC voltages). So it is 115V AC mains voltage and for instance +20V on the power rail of an amplifer.
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Last edited by jean-paul; 15th May 2018 at 09:24 PM.
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Old 16th May 2018, 12:28 AM   #4
FauxFrench is offline FauxFrench  France
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From what you write, I cannot spot an obvious mistake. Such fireworks is rare and does hardly relate to the amplifiers being connected in parallel or turned on without load. For such fireworks much energy is needed and most likely the cause was in the power supply.
Can we have more detailed information on the power supply and the way you connected it?
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Old 16th May 2018, 07:50 AM   #5
rollingreenhills is offline rollingreenhills
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Hi thanks very much for your replies:

I was planning to write about my "success" so I have a blog post and a you tube video:

blog

you tube

So to recap I thought each combination of "rails" (?) on the power supply gave a different AC output. But how would you tell which is live and neutral, perhaps that was the problem? The markings on the rectifiers AC input did not differentiate.
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Old 16th May 2018, 09:38 AM   #6
Khron is offline Khron  Finland
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Rectifiers

In addition to that, digging up the service manual / schematics of that amplifier would also help.
That is, assuming you can't be bothered to try to trace out which pins of that ribbon cable go to what piece of the power circuit.
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Old 16th May 2018, 11:33 AM   #7
jean-paul is offline jean-paul  Netherlands
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Quote:
Originally Posted by rollingreenhills View Post
Hi thanks very much for your replies:

I was planning to write about my "success" so I have a blog post and a you tube video:

blog

you tube

So to recap I thought each combination of "rails" (?) on the power supply gave a different AC output. But how would you tell which is live and neutral, perhaps that was the problem? The markings on the rectifiers AC input did not differentiate.
Oh oh you better start by understanding/learning the basics and then post stuff on the web. You need a schematic of the old amplifier. Something went very wrong, such experiments can cost you your life !

No friend or person you know with more knowledge that can help you out ?
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Old 16th May 2018, 12:00 PM   #8
avtech23 is offline avtech23  Australia
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TPA3116 Disaster - Boom
My guess would be that you had the amplifier board sat in the metal chassis and shorted out the whole thing. Did you record that part too?

Watching your video and reading your blog, being totally honest I'd say:

1. Don't play with mains voltage electronics if you do not know what you are doing (you admit freely that you don't).
2. Take the electronic waste to a proper recycler that doesn't send the waste overseas such as: allgreenrecycling.com/exeter-electronic-waste-recycling/
3. Really, don't play with mains voltage. You might kill yourself, your family, your neighbours.. you get the point. It honestly isn't worth burning your house down or electrocuting someone.
4. If you really want to continue on that path, then get 'overly interested in electronics' and learn enough to know what you are doing, what you need to do and how to keep yourself (and others) safe.
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Old 16th May 2018, 12:02 PM   #9
avtech23 is offline avtech23  Australia
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TPA3116 Disaster - Boom
Also, one of the ebay listings for that amp says:

"This amplifier board must be powered by DC power(DC12-24V), it's better to use high-performance switch power. Don't use transformer!"
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Old 16th May 2018, 12:14 PM   #10
FauxFrench is offline FauxFrench  France
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As a rational engineer, you should first do a damage status. After the fireworks, what seems to be useful to continue with and what is to be thrown away?
Your YouTube video shows a transformer that may still work and some other pieces that could be useful. My impression from what you tell is that the power supply in general belongs to the past. You have to construct a new one, eventually with some old components.

Ready to do that?

You seem to have the gear (Youtube video), I'm convinced you are English (video as well) but one thing confuses me (video), you are in a clearly sunny place. England with sun?!
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