GAIN / TRIM control lets a signal through when it's turned right down?

[studiofreek]

HI. HAVE A PROBLEM WITH MY POWERED MIXER
THE TRIM OR GAIN CONTROL ON ALL THE CHANNELS LETS A SIGNAL THROUGH
EVEN THOUGH ITS TURNED RIGHT DOWN..IT NEVER USED TO DO THIS
CAN ANYONE TELL ME WHAT'S GOING ON HERE. PLEASE

 

[makkem]

HI
AAGH STOP SHOUTING,has the fault made you deaf
Now seriously what make and model of mixer ?
Do you mean a master gain or all of the individual channel gains ?
I take it you mean the gain controls and not the faders.

 

[studiofreek]

HI
AAGH STOP SHOUTING,has the fault made you deaf
Now seriously what make and model of mixer ?
Do you mean a master gain or all of the individual channel gains ?
I take it you mean the gain controls and not the faders.

The mixer amp is a STUDIOMASTER 708 yes it's each channel gain/trim there are 8 on this model
at the top you have gain & at the bottom you have the slider for volume ? I think you call it that..
but it's the same for all 8 channels. I'm sure not too long ago if the gain was rotated anti clock wise ( down ) there was no output to the amps. But now there is..

 

[makkem]

Hi
Although thats a strange fault and the gain control normally does turn the signal off completely that is not the usual way to use the gain control.
What you would normally do is set the fader (slider) at 3/4 of the way up and adjust each gain control in turn to give a VU meter reading of 0 VU,this ensures that each channel is at the same level and then all volume adjustments are done using the fader.
Now the fault.
The component that is the gain control is called a potentiometer and has three connections,signal in,signal out and ground.
When you rotate the control fully one way the signal in and the signal out would be connected with no resistance and you would get full volume,if you rotate fully in the other direction then the signal in would be connected to ground and you would therefore get no signal.
The ground is normally connected to the 0V of the power supply .
So,all I can think is that you have a high resistance in this ground,most likely would be a loose connection somewhere inside the mixer.

 

[studiofreek]

Hi
Although thats a strange fault and the gain control normally does turn the signal off completely that is not the usual way to use the gain control.
What you would normally do is set the fader (slider) at 3/4 of the way up and adjust each gain control in turn to give a VU meter reading of 0 VU,this ensures that each channel is at the same level and then all volume adjustments are done using the fader.
Now the fault.
The component that is the gain control is called a potentiometer and has three connections,signal in,signal out and ground.
When you rotate the control fully one way the signal in and the signal out would be connected with no resistance and you would get full volume,if you rotate fully in the other direction then the signal in would be connected to ground and you would therefore get no signal.
The ground is normally connected to the 0V of the power supply .
So,all I can think is that you have a high resistance in this ground,most likely would be a loose connection somewhere inside the mixer.

Brilliant...you have given me something to check out & I'm thinking that the mixer section may have a bad earth/ground. This would be why all 8 channels have the same fault. have been given the schematics so will investigate.. used the mixer amp today for over 5 hours & set it as best i could & no problems..no peaking
Thanks for your help. will let you know how i go..