Help! Lone Star Special problem

[GeoBull]

Event:
Turned on amp during sound check. It squealed. Swapped some cords around and it stopped (but this was probably coincidence). Started gig using 5 watt setting (my normal setting). During first song volume cut out drastically, then completely. Switched to 30 watt setting. Amp worked. There was a burning smell. Kept playing and finished an hour long set. Burning smell never got worse and then it disapated(sp?). Listened to recording after gig; sound was good. Noticed after gig that I had the back panel Send control way past noon (probably around 3-4 o-clock. I don't ususally do that; I leave it at 12.

Current state:
5-watt = no sound
15-watt = VERY low volume sound
30-watt = normal volume but less headroom than normal
None of the power tubes show any obvious signs of burning
The transformers don't look blown
There isn't any soot, etc. anywhere in the back
Switching out the Rectifier tube with a new one didn't change anything

Thanks in advance for your help.

 

[av8or3]

The fact that you smelled something burning AND have an amp (or part thereof) that dosen't work means that you need to check it in for repairs. Swapping tubes around or twisting knobs will not repair something that has burned.
I don't know what could have happened, it shouldn't matter how the controls are set, the amp should not burn.
You probably won't now what happened until after a tech has a look at it. Sorry....
BTW, I would have it checked out right away, before using it again, to prevent further damage.
Jim

 

[GeoBull]

Thanks for the reply. Because the LSS continued to work on 30-watt and because the fuse didn't blow I assumed it was the rectifier as I've heard that that tube can blow and you're still operable in 30-watt because 30-watt uses the solid-state rectifier. I will take it in for repair.

I took out the chasis and looked inside. There is a small amount of soot on the power tube circuit board where the far right tube (viewing from the back) attaches. Everything else looks normal.

Follow-up question: I live in the Seattle area; there is an authorized repair center here (American Music in Seattle). Time is not an issue; I have an LSC that I can use while I get the LSS repaired.

Do you (or does anybody) have an opinion about whether I should take it to the dealer or simply take out the chasis and send it to Mesa? I.e. do you think authorized repair centers are good enough to do quality work to get this back to where it was?

Thanks again.

 

[ja22y]

If it's a Mesa authorized repair center than you shouldn't have anything to worry about. Sound like the rect tube going bad and it took out the power tube's grid resistor. They can do a mod to fix the rect tube issue for good. good luck and let us know the diagnostic so we can be informed.