TDA 2050 SIGNAL INPUT SECURITY

[rahulrahullll]

------------i made the tda 2050 amplifier played for 30 min-in-low volume----suddenly volume became very

high crackling noise comes out along with song---so switched it off---then checked transformer and tda

2050 ic attached to a big heatsink--slighty warm---then checked power supply everything ok---

then again tried to play song----no sound --but speaker vibrating tremendously as it would burst out

making a booming sound----checked amplifier with another speaker same thing----


------MAIN    ISSUE-------------

---i was using mobile phone and pc 3.5 mm jack output (inbuilt realtek soundcard in motherboard)  as

signal source----after amplifier went wrong---

i used stereo headphones to check signal output of mobile and pc-----sound was coming out-------

---------BUT ONLY MUSIC AND HIGH FREQUENCY sound coming--VOICES IN THE SONG ARE ALMOST GONE JUST ECHOING

SLIGHTLY------------SO THE AMPLIFIER DAMAGED MY PC AND MOBILE PHONE 3.5 MM SOUND OUTPUT-------

---- ---------------------MY  QUERY   IS----------- ------

1----------IS THERE ANYTHING LIKE SIGNAL INPUT SECURITY IN TDA 2050 AMPLIFIER WHICH IN FUTURE WOULD KEEP

MY SIGNAL SOURCE DEVICES PROTECTED IN FUTURE  ?

2----------MY BEST GUESS IS AMPLIFIER FAILED AND SEND POWER DIRECTLY TO SPEAKER AND SOURCE SIGNAL

DEVICES AS PC AND MOBILE so they are damaged------CAN ANYBODY TELL ME WHAT EXACTLY HAPPENED ?




------------------DETAILS OF TDA 2050 BUILD---------------




i made dual rail tda 2050 circuit---according to this----


http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/

pcb diagram----http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/TDA2050-ChipAmp-PCB-

Component-Layout.pdf

parts list----http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/Updated-List-of-

Components-for-PCB.pdf

---------power supply--transformer dual rail---16-0-16 v ac------

22.5-0-22.5 v dc after bridge rectification 10 a and filter capacitor 2200 uf 50 v--------

power circuit looks similiar to this type-values are different--i have used--bridge rectification 10 a-

filter capacitor 2200 uf 50 v

https://cdn.instructables.com/FH7/T1DU/H8RVD01S/FH7T1DUH8RVD01S.MEDIUM.gif



-------------------thank you---------------------

[Zero999]

You made the right decision in using a 16V 0 16V (presumably that's the secondary voltage with no load) transformer. The 18V transformer specified was too high and could give higher than 25V on the rectifiers, when lightly loaded.

Please post a picture showing the actual layout of the circuit you used.

Did you use a heat sink?

Was a proper thermal insulating pad used? If so, is it possible it failed?

Does any of the output current flow through the same wire as the signal? Even though the signal and output share the same ground, it's important that the return side of the output is kept separate from the input. Using star grounding, as mentioned on the site you linked to, will prevent this.

[xani]

Simplest "input protection" would be just a cap but that's already included in input design usually (and probably also in the output of the soundcard). That only prevents DC voltage tho so it would still pass AC spikes. You could possibly add a bunch of diodes (just make sure the voltage is high enough so they do not clip,  ~3-5V should be fine) or back-to-back zeners at the input (before C1)

[wraper]

TDA2050 is not produced for more than 5 years. If you buy one, 99% chance to be counterfeit/knockoff crap rather than old stock. If searched on ebay, most listings have pictures with obvious counterfeits on them. You may post a photo of TDA2050 you have, I will tell if it is an obvious counterfeit or look like genuine.

[rahulrahullll]

-----thank you-------

------right now---amplifier working again everything ok-a  resistor was loose i resoldered it-setup everything--actually  i have a fear in my mind--that  if amplifier chip fails or malfunction sometime---then is it possible that high voltage will enter source signal devices  ?

-----i want to protect my audio signal source devices as pc, mobile-------as you say putting diodes or zener----how exactly i put  them in the +ve signal line  ?

-----------any other security---mainly--for signal source device protection-----and----speaker driver  protection---any simple easy methods----

[Zero999]

Simplest "input protection" would be just a cap but that's already included in input design usually (and probably also in the output of the soundcard). That only prevents DC voltage tho so it would still pass AC spikes. You could possibly add a bunch of diodes (just make sure the voltage is high enough so they do not clip,  ~3-5V should be fine) or back-to-back zeners at the input (before C1)

The amplifier is has a gain of 33 and a power supply voltage of 22.2V, so the output stage will clip, before the input voltage exceeds two diode drops. A bridge rectifier, with the output shorted and a couple of current limiting resistors will do.

[IanMacdonald]

Are you sure you haven't just lost the ground on the 3.5mm jack? That will cause you to have 'subtraction stereo' so the midstage part of the sound will be missing.

Also, I hope you didn't connect both channels of the phone or PC output to one amplifier input. That is equivalent to shorting the outputs, and can damage the source. If you want to use a stereo speaker-level outout with a mono amp, you need to mix the channels with two resistors. Anything from 1k to 10k will do.

Also, NEVER swap the speaker on a malfunctioning direct-coupled amp. If the output is shorted to a supply rail you will destroy a second speaker that way. Check the output pin for DC first. If more than 0.5v or so DO NOT connect a speaker. Or, connect one with an electrolytic in series for test purposes. The cap will prevent the speaker being destroyed if the amp shorts. (of course the cap may pop if it gets sustained reverse bias, but hopefully you've switched off by that time..)

[rahulrahullll]

IanMacdonald---thank you-----i have taken a cable with one end 3.5 mm single jack-inserted to pc-set to 2 channel mode---other side 2 jacks of  which one only i have put  in input of amplifier  other kept hanging---------IS THIS OK  ?

----but right now amplifier sounding ok but my  mobile phone and pc sound out ---mid part voice  missing in songs when used stereo mobile headphones--but if i lightly insert the jack then sounds ok all frequencies----WEIRD----but when i connect to amplifier by 3.5 mm jack (this jack  is bigger in size than the mobile headset) cable all sound frequency ok-----------WEIRDDDDDDDDD--------


-----------------ANY IDEA WHAT IS HAPPENING--------




Hero999-----thank you------i understood circuit ---but  i would like to ask you---what do you think---if amplifier chip fails or malfunction sometime---then is it possible that high voltage will enter source signal devices  ?

---is there any possibility like that  ?

[Zero999]

Yes, if one of the the input transistors on the input goes short circuit (see the internal schematic on page 2 of the data sheet), the input can be dragged down to the negative power supply. The AC coupling capacitor will stop the spike from lasting for a long length of time, but it doesn't take long to damage some ICs.

[rahulrahullll]

thank you--Hero999---right now all issuues resolved everything tightly soldered---------but------

i am using 6 fake china tda 2050-ics-dont know whether they have short circuit protection-very cheap 1 usd for 6 pcs---original 1 usd--- 1 pc  in india---sounding extremely nice-huge volume- i love the sound---but always get scared of my input desktop pc sound source-quite expensive---i want to protect it anyhow---please tell  me what to do---

---so what is ultimate solution to protect input signal device you think--any easy way ?

[Zero999]

The circuit I posted previously, with the four diodes and two resistors, will protect the input source from the amplifier blowing up.