roadster volume problem - ch3 and 4

[Oogadee Boogadee]

Fellas, at rehearsal last night, my amp started giving me problems. The day before, I hooked everything up for a line check and all was good (though, in an apartment, I didn't go a band volume). Then at the rehearsal, ch3 vintage started giving me issues. I didn't have too much time to stop and fiddle with everything... checking wires, trying different modes and wattages and whatnot. decided to switch my rhythm channel to ch4 vintage for a quick fix... but ended up having the same issues. Here's a quick rundown of the events/symptoms.

-set-up my rig
-ch3 set to vintage, 50w, recto tubes
-tuned, using the amp's tuner mute function
-switched to ch3 vintage - no sound.
-bewilderment.
-slowly, within about 10 seconds, and toggling between channels, ch3 came alive.... a bit with a little static I think, and a lot of reluctance
-went through a song - hoping it was a fluke.
-through out the song, i had a hard time hearing ch3.
-ch1 and 2 were fine all night
-began using ch4 vintage as a substitute channel.
-still experienced volume issues. a slow fade out.
-i would toggle to ch2, then back to ch4, then i'd have volume. seemed to act as a 'jumpstart' or something.

in summary, the issues were with 3 and 4, and the channels could get a 'jumpstart' by toggling to 2 or 1.... but it wouldn't last long (30 seconds on average). w/o the jumpstarting, the sound would, if i got lucky, slowly creep back to volume... but not for long. i think it would creep back in, with gain fully engaged - so maybe it's a post pre-amp, pre-power amp issue?

i'm hoping my issues being related to ch3 and ch4 means for an easy cheap fix.... also, i think i remember having the issues on both the diode and rectifer settings, but I dont recall.

Thanks!
James

 

[harem_theater]

sounds like a preamp tube thing...USUALLY but not ALWAYS, if the amp starts buggering on one 'set' on channels then it's obviously the common denominator....

Looking in the back of the manual, the common tubes used for 3&4 are V2 and V3 (one side of V2 and both sides of V3), so i'd look at swapping them out before spending any big cash on getting it looked at.

But i'm just a guitarist so i could be wrong :wink:

 

[gonzald1]

i would like to suggest checking your rectifier tubes also. i had same problem before. I replaced both 5U4G and fixed it.

 

[Oogadee Boogadee]

given what's described in this thread http://forum.grailtone.com/viewtopic.php?f=4&t=25102&start=19 (cathode follower tube info), would replacing my tubes with a doug's tubes tone kit be a waste? I'm curious to experiment, since it appears I have a couple bad tubes anyway. But i don't want to replace them with tubes that will fail fast. What i'm currently running is a Tung-Sol, followed by a complete fleet of Chinese Mesa 12ax7's.

btw Thanks for the input!