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Topic: Fender Twin - Ghost Notes? |
Dave Little
From:
Atlanta
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Posted 5 Feb 2013 5:56 pm |
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My '70 Twin has started singing back to me! Occasionally it will just start sounding a note (harmonic) or series of notes after I've stopped playing. Usually it will either the same note or a harmonic of the loudest note I just played. It's not very loud and doesn't respond to the volume pedal and will only go on for about a minute. The amp will be fine for hours or a few days between these episodes. I had new power tubes installed about 500-600 amp hours ago. The tech said the preamp tubes, caps, etc. looked OK at that time.
Any ideas on what's fixin' to bust?
Dave Little |
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Tim Marcus
From:
San Francisco, CA
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Posted 5 Feb 2013 6:32 pm
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in my experience its usually one of 3 things:
mismatched power tubes
bad filter cap
drifting of values in phase inverter (or tube)
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Milkmansound.com |
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Dave Little
From:
Atlanta
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Posted 5 Feb 2013 6:42 pm
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Looks like a trip to the tech
Thanks
Dave |
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Stephen Cowell
From:
Round Rock, Texas, USA
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Posted 5 Feb 2013 8:47 pm
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Try turning down the reverb... sometimes that can self-oscillate. If so, you can increase the padding around the reverb bag... or make sure the bag's not touching the speaker.
The reverb pan has rubber dampers inside (teeny-tinies inside the transducers) that determine long/short/etc. These can wear out, giving you an ultra-long extra-sensitive reverb tank... that would be prone to self-oscillation. The fix there is to replace the tank.
Sometimes tubes can go microphonic... you can thump lightly on each one and determine if one's gone off. Sometimes you can swap them around... the input tubes are the most sensitive (left-most from the back), you can swap them with others (tremelo etc) and not have to replace them... unless they're all bad.
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Too much junk to list... always getting more. |
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Tim Marcus
From:
San Francisco, CA
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Posted 5 Feb 2013 9:35 pm
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did some more research on ghost notes - might also be a bad filter cap ground
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Milkmansound.com |
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Helmut Gragger
From:
Austria
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Posted 5 Feb 2013 11:11 pm Re: Fender Twin - Ghost Notes?
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| Dave Little wrote: |
| (...)about 500-600 amp hours ago. The tech said the preamp tubes, caps, etc. looked OK at that time. |
Looked ok hundreds of hours ago? Look at the preamp tubes. Tap them with a pencil while running and see if they make noises. Might also be a microphonic preamp tube.
-helmut
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feel at home at: http://me.aquataur.guru |
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