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Chip Amps Amplifiers based on integrated circuits

Blown up TDA2050
Blown up TDA2050
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Old 8th February 2018, 09:24 PM   #1
retvaz is offline retvaz  Argentina
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Default Blown up TDA2050

Hi!
I have recently bought 2x TDA2050 (plus some caps, and a transformer).

I wanted to connect vs+ and vs- to their corresponding pins on the IC, but the ic just blows up after connecting the psu to it.

Im using a 18-0-18 volt 5amp transformer.

I put a bridge rectifier between 18v outputs of the transformer, after that a 4700uf 35v cap between every rail and ground (central tap).

I was getting around 25.5v after rectification so i used extra diodes to lower the voltage a bit and now im getting around 24v after rectifying.

Just for extra security i put a 22k resistor between the cap - side and its corresponding rail, so i was getting around 17,5v bc the caps weren't fully charging.

After that i connected Vs+ to pin 5 and Vs- to pin 3. When i plugged it in a lot of smoke came out of the chip just before it cracked.

Am i doing something wrong? (I know the chips are pretty fake bc they're not in production for couple years but idk).

Any idea?

Thanks guys!

In my run for my first DIY amp i have 2 fried TDA2050 and a fried cellphone :c
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Old 8th February 2018, 10:37 PM   #2
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by retvaz View Post
Just for extra security i put a 22k resistor between the cap - side and its corresponding rail, so i was getting around 17,5v bc the caps weren't fully charging.
In my run for my first DIY amp i have 2 fried TDA2050 and a fried cellphone :c
It is not really clear how you managed to reduce some 24V to 17.5V with a 22KOhm resistor? Or, how your cellphone got fried from all this?

Anyway, a "real" TDA2050 should stand +/-25V so the voltages you mention should not cause the smoke. Unless, your admittedly not genuine TDA2050 is in reality a re-marked TDA2030 that stands only +/-18V (max.).

If you have a variable power supply, it is always clever to start with a lower supply voltage such that you know if the amplifier at least worked with a lower supply voltage. If you only have this fixed voltage supply, you have to take the chance but if it goes wrong, it is difficult afterward to say what happened. Other overload situations can cause the chip to burn such as a DC error at the output, excessive loading or self-oscillation.

You may try with LM1875 in the future as it is very similar to TDA2050. It can be bought at a very reasonable price.

For a class AB amplifier, it is often clever to do the very first test as an idle mode test (preferably at a lower supply voltage) without any input signal and a rather high impedance load at the output. If the amplifier has a DC error at the output, the flaw can be found without a huge current though a low-impedance load.
Only when all measurements indicate a healthy construction, you put a real low-impedance speaker at the output and later an input signal.

Last edited by FauxFrench; 8th February 2018 at 10:45 PM.
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Old 9th February 2018, 12:01 AM   #3
retvaz is offline retvaz  Argentina
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Sadly i dont have a regulable psu nor oscilloscope :c

I reduced the voltage just stacking a bunch of diodes in series, and the resistors were just to prevent the caps from charging too much (So they filter just a bit).

I though i was the one making some error. I'll buy a LM chip next time.



/// My fried phone was because of MY error, this will sound pretty stupid. I was without internet but had a screenshot of a tda2050 schematic, i tried to figure out which pin number was which pin in the IC and connected my input to pin 4. Just fried it :C

Thanks for the answer!
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Old 9th February 2018, 02:11 AM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
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I use 5 watt zener's to lower the power supply voltage to test chip amps.
My test rig power supply is +/-45 volts so is way too high.
The zener's are fine for low volume level testing but I wouldn't be turning the amp up full or you might blow them.
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Old 9th February 2018, 03:27 AM   #5
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by retvaz View Post
Im using a 18-0-18 volt 5amp transformer.

I put a bridge rectifier between 18v outputs of the transformer, after that a 4700uf 35v cap between every rail and ground (central tap).

I was getting around 25.5v after rectification so i used extra diodes to lower the voltage a bit and now im getting around 24v after rectifying.

Just for extra security i put a 22k resistor between the cap - side and its corresponding rail, so i was getting around 17,5v bc the caps weren't fully charging.
Please post a drawing of what you built
Just the power supply for now.
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Old 9th February 2018, 09:09 AM   #6
retvaz is offline retvaz  Argentina
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Click the image to open in full size.
That's a pretty basic schematic. I forget the resistors at the caps but that will do.
When i turned on the PSU the poor TDA just smoked and cracked. Tbh it didnt have a good smell :P

Nigel, thanks for the tip! I didnt know zener diodes could be used for voltage regulation (Im pretty new to electronics sadly).
Thanks to everyone
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Old 10th February 2018, 10:27 PM   #7
PRR is offline PRR  United States
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I believe this chip "MUST" be on a heatsink before full power is applied. The no-signal idle heat is several Watts, and the small chip can only handle a Watt+ without a heatsink.

We almost always connect the several resistors around an amplifier before we apply power, so it "knows" to settle its DC voltages to happy values (about zero on all non-power pins). I do not know what happens if you don't.

I am not clear how you smoked the power chip, with those tiny 1N4148 diodes "dropping". The chip can pass many Amperes. The 1N4148 is rated for 100mA (0.1 Ampere). The power chip's idle current (with normal bias) may be just-about the 1N4148's maximum rating.
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Old 10th February 2018, 10:31 PM   #8
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by retvaz View Post
[IMG]
Nigel, thanks for the tip! I didnt know zener diodes could be used for voltage regulation (Im pretty new to electronics sadly).
Thanks to everyone
Just put the zener's in series with the power supply.
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Old 11th February 2018, 07:42 AM   #9
retvaz is offline retvaz  Argentina
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Oh sorry PRR, i forgot to put the real diodes in there, that was the default model of the schematic software sorry!.

But it is pretty strange, it literally blowed up as soon as i connected it, literally. It was instantaneous. Next time i'll put some resistors and use a zener diode to regulate the supply voltage c:

I'll test with the LM chip next time :_
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Old 11th February 2018, 02:18 PM   #10
Mooly is offline Mooly  United Kingdom
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Blown up TDA2050
I'm not really surprised the IC self destructs when you connect 'just' a power supply to it.

You have to configure it into a valid circuit first.
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