Technika x19/14c-gb-tcd no audio solved .

[petehall347]

desoldered pin 8 from tda1517p then jumped pin 8 to pin 7 . now the audio works fine . even the mute function still works which surprised me .

[R_J]

Re: Technika x19/14c-gb-tcd no audio solved .

The mute function is likely muting the audio signal prior to the input of the tda1517p, Or the mute could be switching the supply voltage on and off, which they do in some models
Pin 7 is the supply voltage for the ic, Pin 8 needs to be above 8.5 volts to turn the ic on, You likely have a fault in the line that controls pin 8

[petehall347]

Re: Technika x19/14c-gb-tcd no audio solved .

seem to remember pin 8 was around 5v .
there seems to be more going on as before the mute wouldn't work before .the icon would come up then disappear and now icon stays on and audio is muted until next press of mute button .
i guess its some crap going on with the audio processor .
an odd thing i noticed with pin 8 whilst its disconnected audio can be injected into it like an audio in.
all academic now as tv back with my friend .it's only a spare waiting for his main tv to stop working altogether . that one reboots itself randomly . thats an old sony abot 40 inch pre digital one that has far more going on inside it than more modern tv.s its that old its silver .

[R_J]

Re: Technika x19/14c-gb-tcd no audio solved .

If you look at the datasheet for the ic, pin8 requires 8.5 volts to turn the ic on, so 5 volts would not have done it. but 5 volts would have brought the ic out of standby (see page 8 of the pdf) Injecting audio into pin 8 likely just turned the ic on.

[petehall347]

Re: Technika x19/14c-gb-tcd no audio solved .

thing is it shouldn't be able to go into mute mode now i shorted it to pin 7 .pin 8 is always high .
ph i confess i did not inject audio .i touched it with my finger and got a nice hum from the speakers .

[R_J]

Re: Technika x19/14c-gb-tcd no audio solved .

The auido output will be fully turned on if you connected pin 7 to pin 8. I suspect the ic is likely ON even when the tv is turned off if the there is voltage on pin 7. The audio will be muted elsewhere, likely with transistors on the input to the ic or in the audio processor ic.
This "mute" function is not to mute the audio but to (internaly) turn off power to the audio output ic to conserve energy. It could also be to prevent a pop in the speakers when the tv is turned on and off
It could be that the voltage going to the ic is always there, even when the tv is in standby and all they do is switch pin 8 on and off.

[petehall347]

Re: Technika x19/14c-gb-tcd no audio solved .

never tested voltage when in standby . i don't think he will really notice his electricity bill being higher .