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I have a Vibrolux made in 1997 and at practice the other night the amp started making a strange noise I have never encountered with a tube amp. The amp has plenty of power but when certain notes are sustained there is a noise on top of the notes like someone is shaking a glass jar full of beads. I have plenty of spare tubes so I replaced all of them including the power tubes ( yes I rebiased ) and the noise is still present. Anyone ever encounter this before.
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Maybe a bad speaker? -
Does it sound like it could be a mechanical rattle, rather than electronic (tubes or a microphonic component)? I've had problems with amps rattling, chassis to cab, handle etc. Even a bad speaker once too. Do you have another speaker cab you can connect to?"In theory, there is no difference between theory and practice. In practice there is."
- Yogi BerraComment
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Yes I tried different speakers, I had mechanical or tube rattles in the past that was resolved with tube dampers etc.. but this sounds really strange I have never heard this before. I was just looking through for cold solder joints and found some really crappy work on the power filter board. The caps are Illinois so I think they are stock but it must have been a friday when they were installed, the blue wire connection was not sticking to the board anymore and was ripping the thin conductive material that is inside the PCB. Same problem with one of the black ground wires. I just finished wiring them directly to the caps leads and will fire her up and let you guys know.Comment
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That didn't work
The plate voltage of V1B is 190vdc, the schematic says 135vdc. I checked the 100k plate load resistor and it's 98k on my dvm.Also it makes the noise in both channels if that helps. I'm getting distortion and unwanted breakup with the volume on 1.Comment
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With the chassis out & on the bench (hooked up to speakers) use a plastic tube or an empty paper towel roll & see if you can't isolate where the noise is coming from while someone else is playing the amp.Comment
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Definately from V1, even playing through the vibrato channel if I apply pressure to the first tube it stops the noise, same results with different tubes. I resoldered all the wires to the socket and cleaned the female parts of the socket.Comment
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So, that fixed the noise.
Right?Comment
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