Quick check with knowledgeable amp folk! (Mesa Lonestar)

MikeB

My Lonestar Classic has recently started with volume drops on Channel 1 and now no sound at all. Given that Channel two and the various wattage modes work fine on Channel 2 I'm assuming its likely to be a preamp tube on Channel 1 that is at fault.

Would I be right in thinking a replacement 12AX7 in position V1 is the best place to start?

Thanks in advance!

ICBM

No, it’s not going to be a valve - there isn’t a stage which is used on Channel 1 and not Channel 2 - the only stage that isn’t shared is an extra one on Channel 2.

It will be a switching problem or something in the control network for Channel 1.

MikeB

Thanks @ICBM will try some things to narrow it down. Thought it might just be a dodgy valve but clearly not from your explanation.

MikeB

Well - seemed to have narrowed it down to the input jack, cable swapped (and pedals removed) and its not that. Seems, when moving the jack in and out of the input socket that the connection comes and goes when turned or removed. Odd since it works just fine on Channel 2 through the same jack socket but clearly some switching or connection on the input jack then as you suggested purely related to Channel 1.

Will review the listed amp repair places in and around Manchester and get it booked in. Doesn't sound like a DIY fix!

jackio

Before you do that, spray contact cleaner into the fx send receive and shove a cable in and out. Known issue but may not be the case given ch2 is fine. But funny things happen

MikeB

jackio said:

Before you do that, spray contact cleaner into the fx send receive and shove a cable in and out. Known issue but may not be the case given ch2 is fine. But funny things happen

Cheers for the tip. Easy to try before I take it to be looked at. Got some contact cleaner knocking about somewhere…….

jackio

Same in the input jack. My LSS does funny stuff (all the lone stars do) when the fx jacks oxidise. Or something. Get dust in them. Who knows but spraying and wiggling sorts that particular issue. Good luck

MikeB

jackio said:

Same in the input jack. My LSS does funny stuff (all the lone stars do) when the fx jacks oxidise. Or something. Get dust in them. Who knows but spraying and wiggling sorts that particular issue. Good luck

Tried some contact cleaner both in the FX loop and the input jack. Don’t help unfortunately. Time to find a repair shop. Cheers for the suggestion though. 

jackio

Shame...

ICBM

It won’t be the jack - there’s no logical reason it could be if the problem is only on one channel. But what could be happening is that a bit of movement of the jack could be flexing the front panel slightly and affecting a bad solder joint or a faulty track contact on one of the pots for channel 1, probably either the gain, treble or master since the whole signal passes through those. (Bass, mid and presence send some frequencies to ground.)

Just a guess, but that’s where I would start looking.

MikeB

Thanks. Found an amp tech and got it booked in for a repair.