muffinresearch
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- Jul 18, 2013
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Hi,
I've got an '81 mk2B, there's an intermittent static background noise sounds like a bad connection or a bad line on a telephone. The noise is irregular crackling, static noise that and comes and goes but is nearly always audible. The noise can be made louder by cranking up the presence which typically I don't have set very high. When the presence is turned down the noise is harder to hear but it's definitely there.
I don't think it's the tubes the preamp and the power-amp tubes have been replaced fairly recently and the noise has persisted despite this.
Fwiw all the PSU electrolytics and the one on the preamp board have been recently replaced for preventative maintenance since the amp is 35years old and all but one of the caps was original.
The noise is there with nothing connected, even when all volume controls are at zero. I have a basic scope setup with a dummy load and I can see the noise there as well as hear it through the speaker.
I've cleaned (with deoxit) and re-tensioned the tube sockets but that doesn't appear to have helped. I've tried to find a loose connection using a plastic tool, but this hasn't yielded anything obvious as yet.
Does anyone have any advice as to what to do next to isolate, and narrow down the source of the noise - or has anyone experienced a similar problem and solved it?
Regards,
Stuart.
I've got an '81 mk2B, there's an intermittent static background noise sounds like a bad connection or a bad line on a telephone. The noise is irregular crackling, static noise that and comes and goes but is nearly always audible. The noise can be made louder by cranking up the presence which typically I don't have set very high. When the presence is turned down the noise is harder to hear but it's definitely there.
I don't think it's the tubes the preamp and the power-amp tubes have been replaced fairly recently and the noise has persisted despite this.
Fwiw all the PSU electrolytics and the one on the preamp board have been recently replaced for preventative maintenance since the amp is 35years old and all but one of the caps was original.
The noise is there with nothing connected, even when all volume controls are at zero. I have a basic scope setup with a dummy load and I can see the noise there as well as hear it through the speaker.
I've cleaned (with deoxit) and re-tensioned the tube sockets but that doesn't appear to have helped. I've tried to find a loose connection using a plastic tool, but this hasn't yielded anything obvious as yet.
Does anyone have any advice as to what to do next to isolate, and narrow down the source of the noise - or has anyone experienced a similar problem and solved it?
Regards,
Stuart.