Another 6505+ troubleshooting thread (please help)

[maddnotez]

So this isn't mine but my other guitarist plugged his NS2 into the Preamp out instead of the FX loop. Ever since then it has been sounding funny. When he did it there was a very loud squeal.

Ever since then it has just sounded weak. Like zero low end, very klank klank. No it is not a Fortin mod, something is definitely wrong but we can't figure it out.

Took it to our local tech. All tubes are good, tech says nothing is wrong. They said it sounded fine on the bench so maybe this is intermittent issue.

The only thing I noticed myself was the grey fuse had a black mark on it. Very mild but I assume if the fuze was bad it wouldn't work at all.

Any ideas? Is it possible to fry something in the preamp when plugging in a pedal to the line out?

 

[jsp]

Not that this is of any help, but I had an old 5150II that pretty much showed the same symptoms, not related to any pedals plugged into it since I never used the loop or preamp out. I tried whatever I read online then, including changing tubes and cleaning all the plugs with contact cleaner. It was also intermittent, but the amp eventually died completely. Instead of getting it fixed I got lazy and gave it away. I hope your guy figures out his issue, though. For whatever it's worth, shortly after, someone told me I should have changed the fuses, including the internal fuse (I wasn't aware there was such a thing).

 

[maddnotez]

Not that this is of any help, but I had an old 5150II that pretty much showed the same symptoms, not related to any pedals plugged into it since I never used the loop or preamp out. I tried whatever I read online then, including changing tubes and cleaning all the plugs with contact cleaner. It was also intermittent, but the amp eventually died completely. Instead of getting it fixed I got lazy and gave it away. I hope your guy figures out his issue, though. For whatever it's worth, shortly after, someone told me I should have changed the fuses, including the internal fuse (I wasn't aware there was such a thing).

Cool thanks.

The fuse thing is what I was thinking but i wasn't sure if it would even turn on or produce any noise with a bad fuse.

 

[jsp]

Yeah, you would think so, but maybe the fuse is marginal rather than just binary open or short, and has some extra resistance before it goes out that is causing the issues.

 

[napalmdeath]

Clean the FX loop inputs. Spray contact cleaner in there, and pop a plug in and out, rinse, & repeat. Both jacks.

 

[311boogieman]

Clean the FX loop inputs. Spray contact cleaner in there, and pop a plug in and out, rinse, & repeat. Both jacks.

I def recommend this except I'd spray the 1/4" jack tip itself and not the socket. And the fuse thing is a good idea too - just happened to me in my multimeter. Meter worked, but gave me messed up readings. Changed the battery - no difference. Looked at the fuse - solid white. Swapped out the fuse - no problem. I have 1a, 2a and 3a fuses here.

Odd that the tech said everything 'sounds' fine. Did he crank it up and give it a good go? Wondering if there is something in your environment that might be causing or adding to this. I'm not an amp tech as you know but I'd be happy to look it over as well. Change that fuse and report back I guess. Which fuse is it?

Really can't think of any reason why sticking line level pedal into the preamp out jack would cause harm.