V- at output.... help me plz!

[weissi]

build up lm3886 as advised in datasheet... feedback resistor is 17k, all other values are as stated in datasheet... feed with +-22V and input is grounded... output voltage is -22V...
checked all connections - >looks that it´s allright... (really!! checked it minimum 10times!)

after first powering up the thing, it went into oscillation mode ;-) (sorry, I didn´t measure the output voltage at this time..)
after that I found out that the gnd rail of the v- capacitor wasn´t connected to gnd.... <- possible reason?? are thr LM´s dead?
connecting an ohmmeter to LM´s pins showed no short circuit to anything... or have I build a comparator? (but +in and -in ARE connected correctly!)

So, please make me happy an tell me what might be wrong...
Thanks!

[Flemming J P]

What have you done with the mute leg?

[weissi]

:-))))))))) left it open... ooopss, ähhh is that important? I´ll try it, report in 20minutes!

I HATE THOSE SHITTY MUTING PINS!!

[weissi]

okay it works now.... I must have known this, had similar problems with the TDA´s.... thought national uses a better muting function - in fact, i didn´t read the datasheet.... I shouldn´t think I know all ;-)

No, the real purpose of my thread was to proof if the forum works in the correct way - to help people


Thank you Flemming!!!

[peranders]

Originally posted by weissi
:-))))))))) left it open... ooopss, ähhh is that important?

Guy's don't you ever try to get hold of datasheets before you use IC's? If you skip reading the "manual" you might miss very important information, like this mute pin. Check also the AN-1192

[weissi]

hey, I´m that type of human, who must try it first, fail, learn, and then get it right... Of course, this method isn´t professional....

Do you know my occupation? you don´t want to know it if you are a person who lost a leg ;-)

nobody´s perfect, and in fact I must make failures to learn something, not by reading books...

forgive me

[li_gangyi]

I'm wondering though...if u mute the pin and it goes -V...wun it kill the speaker there?? If letsae a TV manufacturer were to use the mute pin...what should he (the manaufacturer) do to properly mute the thing??

[weissi]

speaker is - dead - haha, but no problem....
So I´ll go ahead for an active crossover, wich one should, at least in theory, perform better for higher frequency´s and vice versa - TDA7295 or LM3886?

[SkinnyBoy]

Originally posted by li_gangyi
I'm wondering though...if u mute the pin and it goes -V...wun it kill the speaker there?? If letsae a TV manufacturer were to use the mute pin...what should he (the manaufacturer) do to properly mute the thing??

no, cos when the circuit is made correctly the mute pin is never left open, it is always connected to something.... I didn't look at the data sheet so I don't know what, but yeah... lol