Lonestar Classic squeals cant figure it out !

[zeemo]

Hi All,
I just bought a used Lonestar Classic. Love the amp so far
8) except that I
really haven't had a chance to tweak it to my liking .
One thing that concerns me is, I am getting a high pitched noise from it.
the symptoms are as follows:
happens only with the drive channel (loop engaged)
happens without an instrument plugged in.
increases as the drive knob (and the output knob) is turned up
Also is (very) minimal when the drive toggle switch is set to 'normal' but if I try to use either 'thick' or thicker' it becomes more pronounced.
seems to completely go away when I switch the fan off
Thought I might have a monophonic 12ax7 (the one by the fan) so I swapped it (with a used one I had laying around from my F30) - it seems to have diminished but is still there.
I tapped each of the pre amp tubes lightly with a pencil but cant seem to find a blatant 'bad' tube although the tapping can be heard through the amp and speaker on some tubes more than others.
Also I tapped the fromt face of the amp (the chasis I suppose) and I can hear a metallic amplified noise through the speaker.
I guess a set of tubes would be the first move ?
but what about the fan ?
has anyone else experienced this ?? Could it be that the fan is noisy and being amplified somehow through the circuit?
Don't know how to proceed - any advice is extremely welcome.
please don't suggest using 'hard bypass' I really like the distortion channel sound.

ps
called mesa before I did all this troubleshooting like tapping tubes, switching the fan off and on, and swapping the 12ax7 out etc, and the customer service rep seemed to think that it was a bad tube (yes, the one by the fan)

Thanks in advance boogie men!


Zeemo

 

[Mr_You]

Yeah microphonic tube.

 

[zeemo]

Long post for pretty much nothing......... I just D/L the manual and READ it!! I will trouble shoot with a known good tube.

My only concern is that the fan (noise will still be heard) not neccesarily as a loud high pitch, but still be audible.

Thanks for your response.

 

[zeemo]

Another question....
should I stick with stock mesa tubes ??
or is it ok to go with tung-sol or JJ tesla or something in that ballpark ??
Should I be concerned that this is a "class A" design when purchasing tubes ??

Thanks again in advance.

Z

 

[Platypus]

Another question....
should I stick with stock mesa tubes ??
or is it ok to go with tung-sol or JJ tesla or something in that ballpark ??
Should I be concerned that this is a "class A" design when purchasing tubes ??

Thanks again in advance.

Z

Changing from the Mesa tubes will void your warranty (aside from GrooveTubes) but since you bought it used it's probably not a big deal. It sounds like a bad tube to me based on your post. Don't worry about the class A design when purchasing tubes.. just make sure you are getting tubes that are within the operating spec for your amplifier. Any good online tube vendor will be able to point you in the right direction if you tell them what amplifier you have specifically.

 

[zeemo]

Well.... I just bought a set of five JJ tesla 12ax7 s.
This is the type I bought for my F30 when I had a similar problem, (although the symptoms were not the same) they seem to work well, and was a vast improvement over the sound of the F30. I went to the eurotube website and read up on the ones they sell etc. and the different designs.....also I read about jj electronics and they seem to be in the know as far as making quality tubes.
I don't really understand what they mean when they are talking tubes running 'hot' or 'cold' as far as how it relates to bias etc. (actually I dont really understand what bias / fixed bias is) and what the difference is ....
funny thing the F30 had "russian #2" mesa 12ax7 s, and the lonestar had "chinese #1" s just by ignorant hearsay, I would expect that the russian variety would be a better tube......if that's the case, then why would they put a 'lesser' tube in a higher quality / cost amplifier??

anyone have any experience with these jj tesla tube in a lonestar special specifically ??

Thanks again in advance you guys.

Z

 

[zeemo]

Well, problem solved. a bad preamp tube it was indeed !

I had four 12ax7 s that I had replaced on my F-30 (mesa) amp, and kept as spares.

So anyway, I read the manual and going by the symptoms (it was NOT channel specific after all) The high pitched ringing was happening in both channels, so it either had to be V5, which controls phase inverter / driver for both channels, or it was V1 which controls Channel 2 drive stage and input gain stage (for both channels)

It was V1 . No more monophonics.

Just thought I'd share..........

Thanks for your replies. Now I can continue on to enjoy this tone monster !

Later.

Z

 

[Russ]

I know this is a little late but usually V1 gets beat up pretty bad. V1 sets the stage for the rest of the amp's gain stages. I usually try this one first then go to the specific tube responsible for the channel that is causing issues.

 

[nemesys]

V1 does typically take a beating. If you have repeated problems with it, spending a couple of bucks extra on a Mesa SPAX7A for that position can help.

 

[Bikedude]

I've had this problem also. Make sure your loop vol. isn't set too high. I've also re-tubed with JJ pre-amps and EL34's.

 

[TheSon]

Sounds like you have it sorted, but worth mentioning for the info, I had this problem with my RK and it was due to a damaged cable i was using on the FX loop... the lead had a break in it and i found it because the squeel would come and go with moving the lead. new lead, no prob.