Did I burn up my Lonestar?

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MusicMan

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Man what an idiot I am. I was replacing the tubes in my Lonestar and mistankenly put the 5U4 in a 6L6 socket. I had sound until the thing started smoking. OMG! I unplugged it but it kept on smoking. It is obvious that I caused major damage. I pulled the tubes and put them in the correct spots. Amp works but what would I have burned up? I would really like to fix it myself. If I knew where to start. lol Any help would be appreciated. :(
 
Well, it depends on if any pins that are unused on the 6l6 (1 and 6) socket are used as a solder point for anything else. And even then only pin 6 is used in the 5u4. (pin 1 has no connection in either tube).
If not then it might not have done too much to it, but pin 4 is the 'screen' on the 6l6 and the 'plate' (anode) on the 5u4. It may have partially fried the screen resistor (depends how long you left power on after you saw smoke).

Again it would depend on if any unused tube socket (pin) terminals are used for something else which is quite common in amp design. Mesa is not likely to help you with any tech info.
They will tell you to take it to a service station.

If it still works, you "may" be OK, but let's face it, the smoke is not normal...
Good luck :)
 
PS...Also, putting 6 volts on a 5 volt filament (pins 2 and 7) is not too good either, but that depends how robust the filament winding in the power transformer is....and Mesa is usually pretty conservative in their ratings.

Again, a lot depends on how long the power was on when it smoked.
Again, good luck :)
 
Thanks,
Mesa told me it was likely that it fried a (the) screen resistor. If that is the case I could probably replace it (them) myself. I would think just the one is bad. I will take it apart and check. I suppose if the tube doesn't light that would be a dead giveaway.
 
Hopefully that's all.....be aware that the screen resisitor won't affect the filaments, but I know I mentioned it is suspect. Does the tube light? Or any 6l6 in there?

Since the LS takes 6l6 or el34, I believe, the screen resistor should be at least 1000 ohm (1k). it may be as high as 1500 or 1.5k....measure one of the good ones (without tube in socket) to see. A schematic would be great, but don't know where you'd find one for this model.

You may be lucky and that's the only issue........ 8)

As before, good luck with that :)
 
If it's the screen resistor it measures 435 Ohms without the tubes.
But according to the color code it should be a 470 Ohm resistor with 10% tolerance, 3 watts or higher is recommended.

I blew my sreen resistor due to a faulty power tube. It's easy to spot a burnt resistor but might be tricky to remove. It's also a warranty issue, Mesa likes to get mine back for repair!

If you do it yourself make sure to solder it in from above to be on the safe side when the solder joints can't take the tube heat.... There have been issues about desoldered screen resistors on other Mesas..

Rock on!!
 
Yes it is that screen resistor. I bought one and put it in. Amp seems to work fine. Time will tell if I did a good job and got lucky. :D
 
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