Help with Lonestar Classic please

[Pegleg]

I mentioned this problem a while back. Fading of volume together with breakdown of tone in both channels. Seems OK when the amp is first switched on and breaks down after about five minutes of playing. Was previously solved temporarily by switching Standby off and on, but not so easy now. I switched the diode/tube tracking switch earlier and thought I'd cracked it but again not so. I have put in a new set of JJ output tubes. Changed all the 12ax7's one at a time with another that I believe to be good. Back to original set now. The only one I haven't tried is the 5UGB4 rectifier valve. If anything, I do get a bit of a tube 'rattle' from this one and the glow is much dimmer when compared to the new output valves. Does anybody have any fresh ideas, would I get this sort of problem from the rectifier valve ? Unfortunately I don't have a spare to try at the moment. I love this amp but am afraid to gig with it at the moment for fear of reliabilty problems. I sure hope it's just a tube somewhere. Any help would be greatly appreciated.
Thanks

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[Artmusic]

Try switching from the tube rectifier to the solid state rectifier. If the amp works properly then, you may have found your answer.
Art

 

[Pegleg]

I tried that and initially I thought it had solved the problem. However soon after the same occured.

 

[JAZZGEAR]

I have that same problem currently on a 2007 LSC 2x12 Combo I have on loaner from GC until my new one arrives.

However, it only does this in Tweed Mode. It works fine in full power.

WHen first powered on in Tweed, it sounds fine, then the volume fades almost to nothing (in every power mode). Switching to Standy then back on just restarts the same cycle.

I'd look into solving the problem....but I've decided to take this one back tomorrow and swap it for a LSS until my LSC comes in.

 

[Pegleg]

Ok, I 've narrowed it down. The problem doesn't seem to occur in hardbypass mode, but only when the effects loop is switched in. Seems fine for a few mimutes when the amp is first switched in. If I switch to channel two, and then back to one it starts misbehaving ..on both channels. I've changed the V3 FXtube, but it doesn't improve, so I guess it must be an internal problem. Whilst I can at least use the amp in bypass mode, the solo function is too useful to be without. Has anybody else had similar issues and have you managed to solve it simply ?

Cheers.

 

[fishyfishfish]

YES! It was a dirty contact in one of the effects loop jacks. I just plugged a jumper cable in when I wasn't using any effects. Try that and see if it fixes the problem. You can clean the contacts with just a squirt of contact cleaner with the chassis removed, or have a service center do it for you. Should be under warranty.

 

[Pegleg]

Thanks. I spent a couple of hours yesterday digging deep into past threads on this forum. It seems to be a known issue with several of the 'modern era' amps whereby the volume drops out when having the fx loop in (for 'solo' function) with no load on it. (I don't use any fx through the loop). I did indeed put a jumper cable between the send and return and the amp jumped back into life I'm relieved to say Thanks again for your help

Cheers

 

[zappaslaughter]

this is good to know!