session 400 loud buzzzzzzz

[Dave Campbell]

this is probably hard to diagnose on line, but maybe i'll get some starting points...

my session 400 periodically makes a very loud buzz sound. the sound is a lot like grabbing the business end of a 1/4" cable when it's plugged in, but in this case the sounds seem to "take off" more like feedback.

it happens rarely, but when it does it is a real heart stopper. it seems to only happen at high volume, as it has never happened at home.

i have quite a bit of experience with tube amps, but zero with solid state.

[Ricky Davis]

The Power cord is "Grounded" to the Chassis inside; and sounds like it has lost that solder???; but there is a ground stem on the plug end right??? something could of happened with that end of the cord also.
Ricky

[Dave Campbell]

thanks, ricky. i replaced the power cable plug end, which was indeed frayed. i thought i had the problem licked, but last night on the gig the amp was not usable. the feedback aspect of the problem was really evident. even with no input, the amp would kind of take off.

luckily i brought a spare session 400, but i hadn't played it in a while and it needed a good thump to get going....man, the pleasures of old gear!

[Larry Bressington]

Not sure about the session 400, but on the Nashville 400 a common problem was the reverb tank connector, the fix was to unplug it and put some dielectric grease on the connector, problem solved...If you have that white reverb tank plug in connector under the belly of the amp, unplug it and see if the problem goes away.

[Dave Campbell]

i went through all the connections and gave them a clean....it's wired up like an old motorbike! no issues now, but likely they'll appear at the next gig!

[Clyde Mattocks]

I had a similar problem and ordered new filter caps, but before I could install them I went in and cleaned all the molex connections and that cleared up the problem. I have read here on the Forum that those connectors were never designed for this use.

[Dennis Detweiler]

I'm guessing the Molex connectors need to be pulled, crimped and plugged back in. It could also need the two filter caps replaced. When it does it again, use your fist and come down on top of the cabinet and see if it stops.