tda 7293 and tda 7294 help

[sagarverma]

i made two amps with these two
both give a hmmmmm sound in the output and the power indicator leds start blinking
tda 7294 from jean yuveus martin website
tda7293 from elektor 80w schematics

helpppppppppppppppppppppppppppp

[abid_rehan]

Check the ground planes signals, supplies
Which power supply u r using and what about its filtration?
what is the input source?
how the signal from input source is fed to input of power amp?
etc
etc
sorry ol chap ime think u need to provide more detail or check ur circuit for dry solders....

[sagarverma]

i do great soldering.so no question of dry solder.
regarding the amp let me give details.

i m using the power supply the car smps circuit of rod elliots site.it gives me perfect symmetrical +-30v i/p.i am using 10000uf per channel philips caps as filters.
signal is from computer mono out using ultra thin signal wires from a local manufacturer of high repute here in India.

i suppose power supply is the prob and the transformer(the part that i had to manufacture) is at the heart of the problem
is it possible????

a person told me that the ic i m using is altogether fake!!!!!can it be true??can ic be fake
i got ic from same source and built tda1554q and tda8560 and using them in my car with no problem at all

i make po like pcb using photo process so pcb prob also out.

any other that u can make out being culprit

[arasuk]

Hi Sagar,

I have a very bad experince with these chips long time back, had 3 no: of 7294 and blew one after the other.

I suspect that the Ic must be fake. I would suggest you try with LM 3886, it is available easily in the market and high power , better specs.

Arasuk

[abid_rehan]

Hi Sagar:
Though it is highly likely that the chips may be fake, courtesy your south bound neigbours.
However, x-former may also be the heart of the problem (i never have had any problems with this chip, i ve used em in variety of apps, single, parallel, bridge, bridge-parallel) however, do have a look at the x-former.

[sagarverma]

thanks to all for your help
i will take the amp to my college for testing with the pro level power supplies and oscilloscopes.
arasuk.. i dunno y but i love these chips very much.i have brought lm3886 and lm3876 n will test them.but will definately work up on tda729x series.
will inform u guys soon

adhir one question to u."who r my south bound neighbours"?

[sagarverma]

tested the chips at my college.
used the power supply to pwer it up
eureka!!!it worked but at very low volume and heavy noise

college power supply is perfect(no noise,regulated etc etc as with every university)
so what is the noise source
signal source is computer mono out
good quality philips caps used.(original ones from authorised philips outlet)

whats the source
(i tested tda7294 from jean yves martin site pcb link is)
http://www.jeanyvesmartin.com/ampli_TDA7294.htm

[sagarverma]

i used my own power supply(a new 20-0-20) transformer as power source at home and there was SMOKE.my ic's soul disappeared in thin air(tda7293)


anyone has a nice and decent layout that worked.what is schematics?power supply.i have ten of both tda's each so ineed them to work

[sagarverma]

i have now built lm3876tf based amp
it is wonderful.good power and great sound reproduction.but achilles heel is that the ic becomes very hot.load is 4ohm but the prob. continues even eith 8ohm.ihav used it in n.i mode with no cap at i/p signal.the feedback res. is 47k.voltage is very safe 26v at 5amps(power supply is totally clear with fast recifiers and adequate capacitance)
big heat sink that remains cool i.e the ic becomes very hot very soon.is it normal for it?my tda1554q and8563 remained warm during full power
but never as hot(untouchable) as it gets.one more,the ic is tf version i.e insulated version.
thanks in advance for help

[sagarverma]

hi
the circuit was faulty ,i didnt know where was the mistake.so tried another one and its working great.
one thing thats bugging me is that the bass is very weak for it .how can bass be improved for tda7294 chip.