Sansui G6000 scratchy left channel help!!!

[DirtyDog]

I just purchased a Sansui G6000 with a left channel problem.

I can hear music through both channels but the left channel is extremely scratchy and makes very loud popping sounds causing the VU meter to bounce constantly. When I first turn on the receiver the noise is barely there but as it warms up after a few seconds the problem gets progressively worse. These sounds are there regardless of the volume level or input I use.

I am listening through the headphone jack but the speakers show the same problem.

Any ideas as to what the problem might be and if its something easily repairable.

Thanks in advance...

 

[lbcgav]

The first thing to do is clean all the switches and pots.

 

[DirtyDog]

I already cleaned the switches and pots but that is all I have done. Somebody I asked suggested it could be a bad transistor.

 

[DirtyDog]

I asked another person and they also agree it is probably a transistor in the power amp section because it starts happening after the units warms up. Once the units warms up the loud popping and crackling starts and none of the controls affect it.

Are there certain transistors that tend to go bad on these Sansui receivers?

 

[kevzep]

I asked another person and they also agree it is probably a transistor in the power amp section because it starts happening after the units warms up. Once the units warms up the loud popping and crackling starts and none of the controls affect it.

Are there certain transistors that tend to go bad on these Sansui receivers?

Not normally in the G series, but that does not mean one hasn't gone bad, could be a Zener on the front end of the power amp.....hopefully its not the differential FET.
Might be a good time to get the freeze spray out and start hitting some components with that.

 

[DirtyDog]

Not normally in the G series, but that does not mean one hasn't gone bad, could be a Zener on the front end of the power amp.....hopefully its not the differential FET.
Might be a good time to get the freeze spray out and start hitting some components with that.

Thanks for the input. I am just not that knowledgeable about these receivers or which components to check and I am also new to working with electronics. Which components do you think could be the cause?

I swapped the left and right channel output resistors behind the heatsink but the problem remained on the left channel.

 

[kevzep]

Thanks for the input. I am just not that knowledgeable about these receivers or which components to check and I am also new to working with electronics. Which components do you think could be the cause?

I swapped the left and right channel output resistors behind the heatsink but the problem remained on the left channel.

Yeah I think you mean transistors, you need to be careful doing that, the bias ideally would need to be adjusted moving the output transistors around. Those transistors do not normally exhibit such a symptom as you describe, their failure mode is quite different.
It could be anything from a FET to a small signal transistor, to a zener diode, maybe a cap but not that likely, any number of things.
You need a strategy for diagnoses to eliminate components so you do not go around in circles, its not that easy if you are not experienced.
You might get lucky, but then you might not....sometimes problems can be incredibly elusive.

I'd take it to an experienced tech to be honest, you might end up damaging the unit even more than it is now.

 

[DirtyDog]

Yeah I think you mean transistors, you need to be careful doing that, the bias ideally would need to be adjusted moving the output transistors around. Those transistors do not normally exhibit such a symptom as you describe, their failure mode is quite different.
It could be anything from a FET to a small signal transistor, to a zener diode, maybe a cap but not that likely, any number of things.
You need a strategy for diagnoses to eliminate components so you do not go around in circles, its not that easy if you are not experienced.
You might get lucky, but then you might not....sometimes problems can be incredibly elusive.

I'd take it to an experienced tech to be honest, you might end up damaging the unit even more than it is now.

Yes I did mean output transistors and I swapped them back to their original positions so as to not have to adjust the bias.

In any case, I think you are probably right, it will be best to take it an experienced tech.

Thanks for the help