selector switch or volume pot leakage ?

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Brown

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selector switch or volume pot leakage ?
« on: 17 Dec 2008, 04:01 pm »
Ok boys I'm stumped. With the volume control in the off setting still allows the signal to come through at a very low volume. Actually the right channel only. Also notice that the right channel is a tad louder than the left when both vol pots are at the same setting. Tubes are matched and have plenty hours left. No tube problems.
    So do you think its the selector switch or something else.  Thanks for your help I'm clueless.

JoshK

Re: selector switch or volume pot leakage ?
« Reply #1 on: 17 Dec 2008, 04:05 pm »
Is the volume control a pot?  If so, what your observing is bad channel tracking.  Common fault of pots.  Also, with the pot all the way down, there is no gaurantee that attenuation is great enough to be fully "off". 

f2a

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Re: selector switch or volume pot leakage ?
« Reply #2 on: 17 Dec 2008, 05:26 pm »
You can check the pot by changing the out put L&R  of the pot .if the problem move , you can change the pot with new one . ,but I think you should to check  the complete amp circuit with oscilloscope after injection  I khz  af signal  to  aux input and see the  different  in   important point  like  input & out put tube  pins . :thumb:

Brown

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Re: selector switch or volume pot leakage ?
« Reply #3 on: 17 Dec 2008, 06:07 pm »
Is the volume control a pot?  If so, what your observing is bad channel tracking.  Common fault of pots.  Also, with the pot all the way down, there is no gaurantee that attenuation is great enough to be fully "off". 

Yes it is. Thanks Josh for the input.

Brown

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Re: selector switch or volume pot leakage ?
« Reply #4 on: 17 Dec 2008, 06:09 pm »
You can check the pot by changing the out put L&R  of the pot .if the problem move , you can change the pot with new one . ,but I think you should to check  the complete amp circuit with oscilloscope after injection  I khz  af signal  to  aux input and see the  different  in   important point  like  input & out put tube  pins . :thumb:

Thanks f2a. Will try. Lost me with the tube pins. Wired incorrectly ? Dirty? What ? thanks again.

Davey

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Re: selector switch or volume pot leakage ?
« Reply #5 on: 17 Dec 2008, 10:56 pm »
I'll throw my two cents in here.

If your volume potentiometer is configured with the typical connection scheme a bad/open ground (bottom) connection could yield the results you've noted.  (It would vary depending upon the input impedance of the following stage and the resistance of the pot.)

That might explain why you can't get the volume all the way down and the bad channel tracking.

Cheers,

Dave.

Brown

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Re: selector switch or volume pot leakage ?
« Reply #6 on: 18 Dec 2008, 03:54 pm »
I'll throw my two cents in here.

If your volume potentiometer is configured with the typical connection scheme a bad/open ground (bottom) connection could yield the results you've noted.  (It would vary depending upon the input impedance of the following stage and the resistance of the pot.)

That might explain why you can't get the volume all the way down and the bad channel tracking.

Cheers,

Dave.

Thanks Dave. Might just replace the pots with Slagleformers [ Bent ] or a Dact attenuator. Not sure yet.

BobM

Re: selector switch or volume pot leakage ?
« Reply #7 on: 18 Dec 2008, 05:28 pm »
Most pots don't do a very good job of tracking both channels linearly. There always seems to be a lean toward one side or the other. You are better off going with discrete resistors.

Bob