My amplifier burned one of my speakers...

[warning]

Hi guys, As the title of this tread shows I`m having trouble with my new amp. It`s my first amplifier made by me, so I`m beginner and looking for some answers to prevent happening this again.

Here is the schematics I used to made it: 4x15 Watt quad audio amplifier
I made just stereo.

I made it 2 times, 1st time it didn`t worked, because I bought that 4 2R2 resistor, but one of them was just R2, and I didn`t observed. I tried everything I thought may be the problem, because when I turned on one of the speakers not worked, just pulled out the membrane slowly and after about 1-2s it stopped completely. I bought one more ic because I thought that was the problem, and when I demounted the parts from it I saw that r2 thing and my father said that can cause the problem.
I started again, and made again with the same parts, I just used 4 similar resistor, and I when I started it worked, but one of the speaker was a little more quiet, but it worked about 2 minutes, after that the quiet one just stopped working and became so stinky, so I think is burned, but the other one worked correctly. I used the specified parts in correct places, and I used speakers from car, so I don`t think the speaker was to week, or what... I think some of recycled parts was damaged, some of capacitors because that is that I can`t check, but I have no idea which one. or the ic was bad... that I can`t check either.
Somebody can help me to repair my new amp at least?!...

 

[audioguru]

Amplifiers need to be made with a pcb designed by the amplifier IC manufacturer.
American and European car amplifier IC manufacturers show a very good pcb design on their datasheets.
Sometimes a kit manufacturer correctly copies the IC manufacturer's pcb design.
But Toshiba does not show a pcb design on their datasheet and we do not know if the author knows how to correctly design the pcb.
Maybe you should have made a kit that works and has the correct parts values.
Many people do not know that a 2R2 resistor has a value of 2.2 ohms.

You didn't say how you made your amplifier but if you made it on a breadboard then it will probably oscillate and destroy speakers and maybe destroy the IC.

 

[ben7]

The amplifier might have failed, causing your speaker to burn. Maybe, your speaker is cheap, and underrated too.

 

[warning]

audioguru> Right 2R2 is 2.2 ohm, and R2 is 0.2 ohm, sorry. I made my own pcb manually (without computer)using that schematics and I checked 3-4 times, there is no error. The parts are on there places on the right direction, there is no error too. I don`t used breadboard. The only problem I suggest is that I used parts from first one which not worked, maybe one or more part can be damaged, but I don`t know which one. I can change all the parts, but It will not show me what was wrong with it, I want to learn from it.

ben7> My speakers are good enough, car speakers 4 ohm 40w in a home made box so that`s I think enough I used them with another amplifier, and worked just fine until now, the amplifier was the problem I know that for sure but I just want to know what was the problem with that amp because one part worked correctly.

 

[Nigel Goodwin]

As Audioguru asked, did you use the manufacturers recommended PCB layout?, it's usually pretty critical, and a poorly designed PCB coulld easily destroy the amp and your speakers.

Post a picture here of your board.

 

[warning]

But Toshiba does not show a pcb design on their datasheet and we do not know if the author knows how to correctly design the pcb.

I can`t found it too. I have only that schematics that I posted first time.
As I said: One part works fine, other one works, but it is a little more quiet so I have problem not with the pcb, with the parts.

 

[RMMM]

If it got stinky, something is wrong.

Was the output of the amp rated for 4 ohm speakers?

What are you using for an input?

 

[warning]

yes, schematics shows 4 ohm speaker, and the input was connected to my MP3 Player.

 

[RMMM]

Was hooked to a line out or speaker out?

 

[warning]

it have only 1 out, but don`t forget the quiet one burned, the other one worked well. My MP3 is working well, I tested it.

 

[audioguru]

A power amplifier with a pcb layout that allows high current in the resistance of a pcb trace to cause positive feedback produces high frequency oscillation that destroys the speaker and destroys the amplifier.
Audio amplifier ICs have plenty of voltage gain at 4MHz so even a small amount of capacitance coupling between pcb traces will cause high frequency oscillation.

 

[warning]

I found the problem. It is the 4,7u capacitor on that side. I replaced every capacitor on that side one by one and when I changed the 4,7u, it worked all correctly, for a few time until I pushed up the volume on my mp3, then that side stopped again. But I think why that part again, I had just a 4,7u capacitor for smaller voltage, and I think that was the problem. I will change both of 4,7u to a bigger as soon as I can buy them, and I will tell the results.
But it seems a little weird to me... the first one which not worked was for 100v, which one worked was for 63v, but I use 12v only... I assume audioguru had right, and there is a voltage gain, but that much?:S I know 63v is a quiet less then 100v so if it is broken because of voltage gain then ok but for 100v could be enough?!:S I will replace them, but I still think something is not ok with that ic too... Maybe it not likes to be experimented on. Toshiba made it to disagree any troubleshooting to not allow anyone to steal the plans.(I will not replace the ic if it works correctly with 2 capacitor for bigger voltage.)

 

[audioguru]

The 4.7uF capacitors are input coupling capacitors with only about 6V across them. They are polarized and must be connected with the (-) wire at the input and the (+) wire at the IC. if you connected them backwards then of course things get damaged.

 

[warning]

audioguru> I connected correctly both of them(just as you said with (+) to ic, (-) to input).
I still not replaced those capacitors, because the shop closed 10 minutes earlier and here is just one shop...

(My father said to connect a big capacitor in serial with the speakers, and that will protect my speakers from burning, I tried it, and it works fine. I used 2 piece of 1kuf capacitor for 40v. I don`t see any difference in voice using with or without thos caps, but my speakers are stillin good condition, so it works. )

 

[audioguru]

Your input capacitors might have failed because the input source has over 6VDC on it.
Two 1000uF capacitors in series with an 8 ohm speaker reducess 40Hz to half the output power and lower frequencies are reduced more.
Two 1000uF capacitors in series with a 4 ohm speaker reduces 80Hz to half the output power and lower frequencies are reduced more.

The capacitors must be connected back-to-back because when the amplifier fails you do not know the polarity.

 

[warning]

right... I didn`t know that...

I don`t know why, but I changed the 4.7u capacitors to 250v, and it works but... I don`t know how to say how... when I turn it on it works correctly, but after a few second one part shot down, and it is random now, I can`t know which part so the ic must be bad, or I don`t know... :S I had enough of nothing for a few time... I`m looking after new project, maybe later I will come back to this one, but not now... it`s enough... my old amp will be enough for a few more time, but it is old, and so week.

 

[audioguru]

I don't know where on earth you are. I am in Canada so I use mostly American and sometimes I use European ICs. I never use Japanese amplifier ICs. I have never had a problem with an IC.

 

[etofans]

Maybe you got a defective item. You'd better find the seller for solutions.

 

[warning]

I`m in Romania where everything is ****... ok maybe not everything, but almost...
I don`t think the seller can do anything, but even if they can, they will not do anything without money... now I have work to do maybe later I will try again.

 

[RCinFLA]

That is a bridged amplifer.

Besides the previously mentioned oscillations, a bridged amplifier can have a DC offset if there is any leakage on the input side causing a bias offset.

A large DC offset will put a constant current through speakers, maybe enough to heat the voice coil wire.

With no applied input, connect speaker and see if the cone pushes in or out.