Tube question

[Scary]

I'm getting noise, through all channels. It doesn't really get louder when you turn it up, but it's noticable most of the time. Like a fire crackling almost.

I've tried 2 differnt cables, no change. Turned off reverb FX loop and EQ, no change.

Do you guys think it's the first preamp tube?

 

[jpdennis]

I have had this sound before. In my case I just used DeOxit on the sockets, retentioned them, then put back tubes. If the preamp tubes are suspect I would see about using the "replace them one at a time" with a known good one. I even had a V1 which would not take any Mesa preamp tube no matter what. Clean then retention and viola it worked.

Dennis

 

[Scary]

Thanks I just ordered some from sweetwater. I may just try to swap out that first tube while I wait, as it's the original from a pre-500 Mark V.

How do you retension the sockets?

 

[jpdennis]

... How do you retension the sockets? ...

WARNING - The electrolytic capacitors can knock you on your <censored>.  They can also stop your heart.  So be careful!!  If you are not too sure about this then getting a tech to clean and re-tention your sockets might be the most pain-free way to go

Here are some links for just this thing;

Keyed octals;

http://swartamps.com/tech/socket_retention/

Small nine pin but should be the same for the small octals used by 12AX7 or EL84;

http://billmaudio.com/wp/?page_id=171

Read about DeOxit 5 in this link. I found a set of small tools similar to a scratch awl but the size of a jeweler's screwdriver for the 12AX7 sockets. I think you can google "mini pick and hook set".

Dennis

 

[Scary]

I didn't know how to get the covers off of the preamp tubes, so I swapped out the 6L6's with some EL34's I had. Set the bias switch and now the problem is fixed. Thanks for the help.

 

[iceman]

To get the preamp covers off, just push up and turn them. There are bumps on the covers that need to be lined up with notches on the chassis.

 

[Scary]

To get the preamp covers off, just push up and turn them. There are bumps on the covers that need to be lined up with notches on the chassis.

Thanks I didn't see that in the manual.

 

[iceman]

I don't think it is in the manual. For preamp trouble shooting I think they use the same text for each manual... When I first got my roadster and needed to replace a preamp tube it took me awhile to figure it out as well.

 

[udertyrat]

Please don't stick anything in the tube sockets to clean the contacts (if it becomes a problem in the future). You can kill yourself - at least that's my impression. I'm not about to find out the hard way!

I had a problem like the one you mentioned on one of my other amps. I put contact cleaner w/o lubricant on the pins of the tube that went in that socket. Then I put the tube in and out about 10 times. Worked like a charm... and no electrocution!

Hope it helps.