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5150 with intermittently loud "swooshing" sound..please help


stigmataguitar

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I have a Patent Pending block letter 5150 that has started to develope a loud "swooshing" type sound. The amp will play fine for awhile and then out of nowhere the swooshing will start. I can then power it down and restart but upon repowering the amp the swoosh is is somethimes still there immediately after taking off standby. This amp was bought from Brad Whitford of Aerosmith and had been used quite a bit in the early 90's. The only known issue with this amp was a burnt ribbon cable which was repaired by Brad's amp tech Greg Howard. I have tried new tubes throughout but problem is still there. Anyone have any ideas of what is causing this problem?

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Does it have a kind of wind on am icrphone sound? I had a screw that holds a rubber grommet to the back of the preamp board start shorting out against the traces on the pre board and it got worse and worse until the amp stopped working at all. Pretty weird. Had to move it out of the way away from the traces and it worked fine again.

 

screw3b.jpg

You can see where it melted the traces.

 

 

But generally stuff like this is tube-related. I'd check that first.

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Does it have a kind of wind on am icrphone sound? I had a screw that holds a rubber grommet to the back of the preamp board start shorting out against the traces on the pre board and it got worse and worse until the amp stopped working at all. Pretty weird. Had to move it out of the way away from the traces and it worked fine again.


screw3b.jpg
You can see where it melted the traces.



But generally stuff like this is tube-related. I'd check that first.

 

Thanks for the picture! I opened it up a couple hours ago and the bumper was definatly touching the board a bit so I took the bumper off and sanded it down a little. I also disconnected and reconneceted the ribbon cables to clean their connections along with cleaning all tube sockets, pots and jacks. Placed back into it's headshell along with all new tubes and so far so good! The amp has been on for the past hour with no problems yet! :thu:

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Thanks for the picture! I opened it up a couple hours ago and the bumper was definatly touching the board a bit so I took the bumper off and sanded it down a little. I also disconnected and reconneceted the ribbon cables to clean their connections along with cleaning all tube sockets, pots and jacks. Placed back into it's headshell along with all new tubes and so far so good! The amp has been on for the past hour with no problems yet!
:thu:

 

The bumper is supposed to touch the board. It supports it when you put tubes in it. I bet it was tube related. I've never heard of anyone else having that problem. :idk:

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The bumper is supposed to touch the board. It supports it when you put tubes in it. I bet it was tube related. I've never heard of anyone else having that problem.
:idk:

 

I'm thinking it was either a tube or a dirty ribbon cable connection since a couple of connection pins had what looked like a slight hint of corrosion on them.

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