Cuts to low volume

iFreedom · Sep 4, 2009

My combo that i've had for about 3 months seems to have issues. Last night, the volume cut back 3 times to very low volume, but still had all the gain, but was just very quiet. So immediately I thought my pwoer tubes and I looked at them and the they were glowing blue. But it turns out blue glowing tubes (original mesa 6l6's) are not indicative of bad tubes at all. Also, it would cut back to regular volume in less than a minute and run fine for a while. One of the other times it cut back, I switch to variac mode and it was fine, so I put it back to full power and it was still fine, but later cut back to low volume for less than a minute and was fine again. I jammed for about an hour, and it cut back 3 times (never happened before) so overall it ran at a cut back volume for maybe 3 minutes.

Tonight I am going to check my cables but I suspect it's the amp or maybe my power supply as I run thru a power bar (have for years though).

I used to own and gig with a jcm 2000 and never ever had tube / amp problems, so I'm definetly a noob to troubleshooting amp issues.

Anyone else run into this with their V?

gplex · Sep 4, 2009

Loss of volume is almost always a power tube issue. I would get a new set of tubes to try. If they are not the problem, save them for a later date. If thats all it is, you saved yourself the trouble of sending it out for repair and the down time associated.

Power tubes go out one of two way's.

A gradual loss of volume, flickering volume, loss of tone.
OR
In a violent flash causing extremely high current draw and blown fuses.

dodger916 · Sep 4, 2009

Could it be a failing phase inverter?
Also, what amp?

AdamL1 · Sep 14, 2009

Same thing over here, volume cuts to 30% and solo switch stops working, it's intermittent and happens any time for the last 2 days. this is my second mk-5 first one shorted on channel 3 when eq was engaged.
My mesa dealer replaced it for me, now he doesn't have any more in stock

Adam
Montreal, Canada

MusicManJP6 · Sep 14, 2009

Bad tubes seem to plague this amp. Swap tubes one at a time...

iFreedom · Sep 22, 2009

Actually, it seems to be something with the effects loop. As I jiggle the cable, I was able to replicate this low volume stuff, so maybe it's my cables, or maybe something wrong with my loop.

Also, switching off the fx on the foot controller reveals the high-cut when it is on. Now, I read this in the manual, but I never noticed this before. Am I going crazy or what? The difference between on and off on the fx is night and day now - I swear it wasn't like that before. The manual says that cheap fx cause a high freq roll off.

phyrexia · Sep 22, 2009

try sticking a cable in between the send and return jacks of the loop. try cycling the loop select switch. try moving the fx send level knob back and forth to get rid of any dirt that may have gotten in there.