Rectoverb Volume Fluctuations - Help!!!!

[same313]

Hi there,

I was wondering if anyone could help me with a problem I am experiencing with my 6 month old Rectoverb. I am experiencing slight fluctuations in volume when playing and I was wondering whether this was normal due to the Boogie slightly compressing the signal or whether I need to get it checked out. It occurs without anything plugged into the fx loop etc. There also seems to be some rattling in the speaker or amp casing when playing certain notes on my guitar (E and F on the 5th string). It doesnt seem to be resonating too much on my guitar strings and again I was wondering if my precious Boogie is poorly!

Thanks guys!

Sam Eads

 

[domct203]

Could be the "Cathode Follower" senerio.

Quoted from this post http://forum.grailtone.com/viewtopic.php?f=4&t=25102

Hey Blakkspider, I hope that you got your amp back up and running. Here's the info from the Mesa Memo...


SOUND “DROP-OUTS” / INTERMITTENT SIGNAL

One Possible Cause



Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.



Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.



For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.



In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).



Below is a partial list of Mesa amps and cathode follower tube locations:

GUITAR AMPS BASS AMPS

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.

Good Luck.

Dom

 

[same313]

Hi Dom!

Thanks for the reply. I bought my Mesa new so no one messed with the tubes prior to the sale but I'll check them out nevertheless. I was told by the dealer that I may have been driving the pre-amp a little too hard with my channel volumes on 3/4+ and the master on 1/4, so I've changed all the settings to the recommended ones and I havnt had a problem with it today so far. Typical!!!

Thanks anyway! Any more suggestions would be much appreciated if anyone else has experienced this phenomenon!

Sam