Mini Recto - Volume drops

[PaulJam]

Hello,

I have a problem with my Mini Rectifier. I've been playing both channels in 10W mode with fairly low bedroom volume.
In the last few days i had this problem, where the sound in Ch. 2 suddenly cuts off for a short while - a slight signal is still coming through as if you roll the volume pot completely down (I've heard thats normal?). Today after playing for about 45 minutes the volume dropped again, but didn't come back. I switched to 25W mode and the volume was back at normal. Back at 10W the volume was gone again (as if you roll the volume completely down). In the clean channel (10W) the sound was clipping although the channel is set clean to not break up at all.

I would appreciate if you could help me fix this problem.
Thanks.

 

[brich]

It sounds like you need to replace the preamp tubes. My Single Rec had a similar issue and it was a bad 12AX7 in V1. That is the cheapest, easiest place to start.

 

[PaulJam]

Thanks for the reply.

What I don't understand is, that after i turned off the amp and waited for about half an hour everything worked normal. Now it appears every twenty to thirty minutes that the sound will cut off and the immediately come back. So can this really be a tube related problem?

 

[brich]

It is possible. Mine did the same thing. It would go several days of working fine then cut back out again. I would power it off and it would work fine after turning it back on. I put new tubes a few months ago and it has been working just fine ever since.

 

[Gnarkill3k6]

Maybe this helps: http://forum.grailtone.com/viewtopic.php?f=4&t=25102&start=19

 

[elvis]

It may help to understand that vacuum tubes are more mechanical than electrical devices. The spacings of all the metal components are critical, as is the temperature. A tube may fail at one temperature but not another due to expansion and contraction. In addition, the tubes are heated with an internal filament. As they heat, a broken wire or contact may expand and break contact, or make contact, such that the tube doesn't work for a while, and then does work.

Intermittent problems are very common in tubes. It doesn't help that they tend to be located on top of vibrating speaker cabinets, and that the amps get handled roughly at times, despite the owners' best intentions.

 

[Addictedtokaos]

Maybe this helps: http://forum.grailtone.com/viewtopic.php?f=4&t=25102&start=19

Its been confirmed from Mesa that the mini do not have cathode follower like the 50/100/150w. Not saying its not a preamp tube but this doesnt apply to the mini.

 

[PaulJam]

Hello me again
So I think I narrowed the Problem down.It happens in channel two 10 Watt mode after about 30-45 minutes that the sound will cut off only for a short amount of time.When switched to 25 Watt every channel and mode will work just fine.
I have ordered some new Tubes 1 Tung Sol 12ax7 1 Mesa branded 12ax7 and some Mesa EL84´s (color code Green).
I installed the Tung Sol in V1 but it happened again.
Now I am changing the Power Tubes,any other suggestions?

Thanks for your help

 

[elvis]

I would guess PI (V4) or power tubes. I'm leaning toward power tubes since they work fine in 25W mode.

 

[hugoadrian]

Hello guys!!
I had the same problem with my amp, what was the deal? Should I replace a 12AX7?